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<!doctype html> <html lang="en"> <head> <meta charset="utf-8"> <meta name="viewport" content="width=device-width"> <title>Buffer | Node.js v10.19.0 Documentation</title> <link rel="stylesheet" href="assets/style.css"> <link rel="stylesheet" href="assets/sh.css"> <link rel="canonical" href="buffer.html"> </head> <body class="alt apidoc" id="api-section-buffer"> <div id="content" class="clearfix"> <div id="column2" class="interior"> <div id="intro" class="interior"> <a href="/" title="Go back to the home page"> Node.js </a> </div> <ul> <li><a class="nav-documentation" href="documentation.html">About these Docs</a></li> <li><a class="nav-synopsis" href="synopsis.html">Usage & Example</a></li> </ul> <div class="line"></div> <ul> <li><a class="nav-assert" href="assert.html">Assertion Testing</a></li> <li><a class="nav-async_hooks" href="async_hooks.html">Async Hooks</a></li> <li><a class="nav-buffer active" href="buffer.html">Buffer</a></li> <li><a class="nav-addons" href="addons.html">C++ Addons</a></li> <li><a class="nav-n-api" href="n-api.html">C/C++ Addons - N-API</a></li> <li><a class="nav-child_process" href="child_process.html">Child Processes</a></li> <li><a class="nav-cluster" href="cluster.html">Cluster</a></li> <li><a class="nav-cli" href="cli.html">Command Line Options</a></li> <li><a class="nav-console" href="console.html">Console</a></li> <li><a class="nav-crypto" href="crypto.html">Crypto</a></li> <li><a class="nav-debugger" href="debugger.html">Debugger</a></li> <li><a class="nav-deprecations" href="deprecations.html">Deprecated APIs</a></li> <li><a class="nav-dns" href="dns.html">DNS</a></li> <li><a class="nav-domain" href="domain.html">Domain</a></li> <li><a class="nav-esm" href="esm.html">ECMAScript Modules</a></li> <li><a class="nav-errors" href="errors.html">Errors</a></li> <li><a class="nav-events" href="events.html">Events</a></li> <li><a class="nav-fs" href="fs.html">File System</a></li> <li><a class="nav-globals" 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class="nav-stream" href="stream.html">Stream</a></li> <li><a class="nav-string_decoder" href="string_decoder.html">String Decoder</a></li> <li><a class="nav-timers" href="timers.html">Timers</a></li> <li><a class="nav-tls" href="tls.html">TLS/SSL</a></li> <li><a class="nav-tracing" href="tracing.html">Trace Events</a></li> <li><a class="nav-tty" href="tty.html">TTY</a></li> <li><a class="nav-dgram" href="dgram.html">UDP/Datagram</a></li> <li><a class="nav-url" href="url.html">URL</a></li> <li><a class="nav-util" href="util.html">Utilities</a></li> <li><a class="nav-v8" href="v8.html">V8</a></li> <li><a class="nav-vm" href="vm.html">VM</a></li> <li><a class="nav-worker_threads" href="worker_threads.html">Worker Threads</a></li> <li><a class="nav-zlib" href="zlib.html">Zlib</a></li> </ul> <div class="line"></div> <ul> <li><a class="nav-https-github-com-nodejs-node" href="https://github.com/nodejs/node">GitHub Repo & Issue Tracker</a></li> </ul> </div> <div id="column1" data-id="buffer" class="interior"> <header> <h1>Node.js v10.19.0 Documentation</h1> <div id="gtoc"> <ul> <li> <a href="index.html" name="toc">Index</a> </li> <li> <a href="all.html">View on single page</a> </li> <li> <a href="buffer.json">View as JSON</a> </li> <li class="version-picker"> <a href="#">View another version <span>▼</span></a> <ol class="version-picker"><li><a href="https://nodejs.org/docs/latest-v12.x/api/buffer.html">12.x</a></li> <li><a href="https://nodejs.org/docs/latest-v11.x/api/buffer.html">11.x</a></li> <li><a href="https://nodejs.org/docs/latest-v10.x/api/buffer.html">10.x <b>LTS</b></a></li> <li><a href="https://nodejs.org/docs/latest-v9.x/api/buffer.html">9.x</a></li> <li><a href="https://nodejs.org/docs/latest-v8.x/api/buffer.html">8.x <b>LTS</b></a></li> <li><a href="https://nodejs.org/docs/latest-v7.x/api/buffer.html">7.x</a></li> <li><a href="https://nodejs.org/docs/latest-v6.x/api/buffer.html">6.x</a></li> <li><a href="https://nodejs.org/docs/latest-v5.x/api/buffer.html">5.x</a></li> <li><a href="https://nodejs.org/docs/latest-v4.x/api/buffer.html">4.x</a></li> <li><a href="https://nodejs.org/docs/latest-v0.12.x/api/buffer.html">0.12.x</a></li> <li><a href="https://nodejs.org/docs/latest-v0.10.x/api/buffer.html">0.10.x</a></li></ol> </li> <li class="edit_on_github"><a href="https://github.com/nodejs/node/edit/master/doc/api/buffer.md"><span class="github_icon"><svg height="16" width="16" viewBox="0 0 16.1 16.1" fill="currentColor"><path d="M8 0a8 8 0 0 0-2.5 15.6c.4 0 .5-.2.5-.4v-1.5c-2 .4-2.5-.5-2.7-1 0-.1-.5-.9-.8-1-.3-.2-.7-.6 0-.6.6 0 1 .6 1.2.8.7 1.2 1.9 1 2.4.7 0-.5.2-.9.5-1-1.8-.3-3.7-1-3.7-4 0-.9.3-1.6.8-2.2 0-.2-.3-1 .1-2 0 0 .7-.3 2.2.7a7.4 7.4 0 0 1 4 0c1.5-1 2.2-.8 2.2-.8.5 1.1.2 2 .1 2.1.5.6.8 1.3.8 2.2 0 3-1.9 3.7-3.6 4 .3.2.5.7.5 1.4v2.2c0 .2.1.5.5.4A8 8 0 0 0 16 8a8 8 0 0 0-8-8z"/></svg></span>Edit on GitHub</a></li> </ul> </div> <hr> </header> <div id="toc"> <h2>Table of Contents</h2> <ul> <li><span class="stability_2"><a href="#buffer_buffer">Buffer</a></span><ul> <li><a href="#buffer_buffer_from_buffer_alloc_and_buffer_allocunsafe"><code>Buffer.from()</code>, <code>Buffer.alloc()</code>, and <code>Buffer.allocUnsafe()</code></a><ul> <li><a href="#buffer_the_zero_fill_buffers_command_line_option">The <code>--zero-fill-buffers</code> command line option</a></li> <li><a href="#buffer_what_makes_buffer_allocunsafe_and_buffer_allocunsafeslow_unsafe">What makes <code>Buffer.allocUnsafe()</code> and <code>Buffer.allocUnsafeSlow()</code> "unsafe"?</a></li> </ul> </li> <li><a href="#buffer_buffers_and_character_encodings">Buffers and Character Encodings</a></li> <li><a href="#buffer_buffers_and_typedarray">Buffers and TypedArray</a></li> <li><a href="#buffer_buffers_and_iteration">Buffers and iteration</a></li> <li><a href="#buffer_class_buffer">Class: Buffer</a><ul> <li><span class="stability_0"><a href="#buffer_new_buffer_array">new Buffer(array)</a></span></li> <li><span class="stability_0"><a href="#buffer_new_buffer_arraybuffer_byteoffset_length">new Buffer(arrayBuffer[, byteOffset[, length]])</a></span></li> <li><span class="stability_0"><a href="#buffer_new_buffer_buffer">new Buffer(buffer)</a></span></li> <li><span class="stability_0"><a href="#buffer_new_buffer_size">new Buffer(size)</a></span></li> <li><span class="stability_0"><a href="#buffer_new_buffer_string_encoding">new Buffer(string[, encoding])</a></span></li> <li><a href="#buffer_class_method_buffer_alloc_size_fill_encoding">Class Method: Buffer.alloc(size[, fill[, encoding]])</a></li> <li><a href="#buffer_class_method_buffer_allocunsafe_size">Class Method: Buffer.allocUnsafe(size)</a></li> <li><a href="#buffer_class_method_buffer_allocunsafeslow_size">Class Method: Buffer.allocUnsafeSlow(size)</a></li> <li><a href="#buffer_class_method_buffer_bytelength_string_encoding">Class Method: Buffer.byteLength(string[, encoding])</a></li> <li><a href="#buffer_class_method_buffer_compare_buf1_buf2">Class Method: Buffer.compare(buf1, buf2)</a></li> <li><a href="#buffer_class_method_buffer_concat_list_totallength">Class Method: Buffer.concat(list[, totalLength])</a></li> <li><a href="#buffer_class_method_buffer_from_array">Class Method: Buffer.from(array)</a></li> <li><a href="#buffer_class_method_buffer_from_arraybuffer_byteoffset_length">Class Method: Buffer.from(arrayBuffer[, byteOffset[, length]])</a></li> <li><a href="#buffer_class_method_buffer_from_buffer">Class Method: Buffer.from(buffer)</a></li> <li><a href="#buffer_class_method_buffer_from_object_offsetorencoding_length">Class Method: Buffer.from(object[, offsetOrEncoding[, length]])</a></li> <li><a href="#buffer_class_method_buffer_from_string_encoding">Class Method: Buffer.from(string[, encoding])</a></li> <li><a href="#buffer_class_method_buffer_isbuffer_obj">Class Method: Buffer.isBuffer(obj)</a></li> <li><a href="#buffer_class_method_buffer_isencoding_encoding">Class Method: Buffer.isEncoding(encoding)</a></li> <li><a href="#buffer_class_property_buffer_poolsize">Class Property: Buffer.poolSize</a></li> <li><a href="#buffer_buf_index">buf[index]</a></li> <li><a href="#buffer_buf_buffer">buf.buffer</a></li> <li><a href="#buffer_buf_byteoffset">buf.byteOffset</a></li> <li><a href="#buffer_buf_compare_target_targetstart_targetend_sourcestart_sourceend">buf.compare(target[, targetStart[, targetEnd[, sourceStart[, sourceEnd]]]])</a></li> <li><a href="#buffer_buf_copy_target_targetstart_sourcestart_sourceend">buf.copy(target[, targetStart[, sourceStart[, sourceEnd]]])</a></li> <li><a href="#buffer_buf_entries">buf.entries()</a></li> <li><a href="#buffer_buf_equals_otherbuffer">buf.equals(otherBuffer)</a></li> <li><a href="#buffer_buf_fill_value_offset_end_encoding">buf.fill(value[, offset[, end]][, encoding])</a></li> <li><a href="#buffer_buf_includes_value_byteoffset_encoding">buf.includes(value[, byteOffset][, encoding])</a></li> <li><a href="#buffer_buf_indexof_value_byteoffset_encoding">buf.indexOf(value[, byteOffset][, encoding])</a></li> <li><a href="#buffer_buf_keys">buf.keys()</a></li> <li><a href="#buffer_buf_lastindexof_value_byteoffset_encoding">buf.lastIndexOf(value[, byteOffset][, encoding])</a></li> <li><a href="#buffer_buf_length">buf.length</a></li> <li><span class="stability_0"><a href="#buffer_buf_parent">buf.parent</a></span></li> <li><a href="#buffer_buf_readdoublebe_offset">buf.readDoubleBE(offset)</a></li> <li><a href="#buffer_buf_readdoublele_offset">buf.readDoubleLE(offset)</a></li> <li><a href="#buffer_buf_readfloatbe_offset">buf.readFloatBE(offset)</a></li> <li><a href="#buffer_buf_readfloatle_offset">buf.readFloatLE(offset)</a></li> <li><a href="#buffer_buf_readint8_offset">buf.readInt8(offset)</a></li> <li><a href="#buffer_buf_readint16be_offset">buf.readInt16BE(offset)</a></li> <li><a href="#buffer_buf_readint16le_offset">buf.readInt16LE(offset)</a></li> <li><a href="#buffer_buf_readint32be_offset">buf.readInt32BE(offset)</a></li> <li><a href="#buffer_buf_readint32le_offset">buf.readInt32LE(offset)</a></li> <li><a href="#buffer_buf_readintbe_offset_bytelength">buf.readIntBE(offset, byteLength)</a></li> <li><a href="#buffer_buf_readintle_offset_bytelength">buf.readIntLE(offset, byteLength)</a></li> <li><a href="#buffer_buf_readuint8_offset">buf.readUInt8(offset)</a></li> <li><a href="#buffer_buf_readuint16be_offset">buf.readUInt16BE(offset)</a></li> <li><a href="#buffer_buf_readuint16le_offset">buf.readUInt16LE(offset)</a></li> <li><a href="#buffer_buf_readuint32be_offset">buf.readUInt32BE(offset)</a></li> <li><a href="#buffer_buf_readuint32le_offset">buf.readUInt32LE(offset)</a></li> <li><a href="#buffer_buf_readuintbe_offset_bytelength">buf.readUIntBE(offset, byteLength)</a></li> <li><a href="#buffer_buf_readuintle_offset_bytelength">buf.readUIntLE(offset, byteLength)</a></li> <li><a href="#buffer_buf_slice_start_end">buf.slice([start[, end]])</a></li> <li><a href="#buffer_buf_swap16">buf.swap16()</a></li> <li><a href="#buffer_buf_swap32">buf.swap32()</a></li> <li><a href="#buffer_buf_swap64">buf.swap64()</a></li> <li><a href="#buffer_buf_tojson">buf.toJSON()</a></li> <li><a href="#buffer_buf_tostring_encoding_start_end">buf.toString([encoding[, start[, end]]])</a></li> <li><a href="#buffer_buf_values">buf.values()</a></li> <li><a href="#buffer_buf_write_string_offset_length_encoding">buf.write(string[, offset[, length]][, encoding])</a></li> <li><a href="#buffer_buf_writedoublebe_value_offset">buf.writeDoubleBE(value, offset)</a></li> <li><a href="#buffer_buf_writedoublele_value_offset">buf.writeDoubleLE(value, offset)</a></li> <li><a href="#buffer_buf_writefloatbe_value_offset">buf.writeFloatBE(value, offset)</a></li> <li><a href="#buffer_buf_writefloatle_value_offset">buf.writeFloatLE(value, offset)</a></li> <li><a href="#buffer_buf_writeint8_value_offset">buf.writeInt8(value, offset)</a></li> <li><a href="#buffer_buf_writeint16be_value_offset">buf.writeInt16BE(value, offset)</a></li> <li><a href="#buffer_buf_writeint16le_value_offset">buf.writeInt16LE(value, offset)</a></li> <li><a href="#buffer_buf_writeint32be_value_offset">buf.writeInt32BE(value, offset)</a></li> <li><a href="#buffer_buf_writeint32le_value_offset">buf.writeInt32LE(value, offset)</a></li> <li><a href="#buffer_buf_writeintbe_value_offset_bytelength">buf.writeIntBE(value, offset, byteLength)</a></li> <li><a href="#buffer_buf_writeintle_value_offset_bytelength">buf.writeIntLE(value, offset, byteLength)</a></li> <li><a href="#buffer_buf_writeuint8_value_offset">buf.writeUInt8(value, offset)</a></li> <li><a href="#buffer_buf_writeuint16be_value_offset">buf.writeUInt16BE(value, offset)</a></li> <li><a href="#buffer_buf_writeuint16le_value_offset">buf.writeUInt16LE(value, offset)</a></li> <li><a href="#buffer_buf_writeuint32be_value_offset">buf.writeUInt32BE(value, offset)</a></li> <li><a href="#buffer_buf_writeuint32le_value_offset">buf.writeUInt32LE(value, offset)</a></li> <li><a href="#buffer_buf_writeuintbe_value_offset_bytelength">buf.writeUIntBE(value, offset, byteLength)</a></li> <li><a href="#buffer_buf_writeuintle_value_offset_bytelength">buf.writeUIntLE(value, offset, byteLength)</a></li> </ul> </li> <li><a href="#buffer_buffer_inspect_max_bytes">buffer.INSPECT_MAX_BYTES</a></li> <li><a href="#buffer_buffer_kmaxlength">buffer.kMaxLength</a></li> <li><a href="#buffer_buffer_transcode_source_fromenc_toenc">buffer.transcode(source, fromEnc, toEnc)</a></li> <li><span class="stability_0"><a href="#buffer_class_slowbuffer">Class: SlowBuffer</a></span><ul> <li><span class="stability_0"><a href="#buffer_new_slowbuffer_size">new SlowBuffer(size)</a></span></li> </ul> </li> <li><a href="#buffer_buffer_constants">Buffer Constants</a><ul> <li><a href="#buffer_buffer_constants_max_length">buffer.constants.MAX_LENGTH</a></li> <li><a href="#buffer_buffer_constants_max_string_length">buffer.constants.MAX_STRING_LENGTH</a></li> </ul> </li> </ul> </li> </ul> </div> <div id="apicontent"> <h1>Buffer<span><a class="mark" href="#buffer_buffer" id="buffer_buffer">#</a></span></h1> <!--introduced_in=v0.1.90--> <div class="api_stability api_stability_2"><a href="documentation.html#documentation_stability_index">Stability: 2</a> - Stable</div><p>Prior to the introduction of <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a>, the JavaScript language had no mechanism for reading or manipulating streams of binary data. The <code>Buffer</code> class was introduced as part of the Node.js API to enable interaction with octet streams in TCP streams, file system operations, and other contexts.</p> <p>With <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a> now available, the <code>Buffer</code> class implements the <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array"><code>Uint8Array</code></a> API in a manner that is more optimized and suitable for Node.js.</p> <p>Instances of the <code>Buffer</code> class are similar to arrays of integers but correspond to fixed-sized, raw memory allocations outside the V8 heap. The size of the <code>Buffer</code> is established when it is created and cannot be changed.</p> <p>The <code>Buffer</code> class is within the global scope, making it unlikely that one would need to ever use <code>require('buffer').Buffer</code>.</p> <pre><code class="language-js">// Creates a zero-filled Buffer of length 10. const buf1 = Buffer.alloc(10); // Creates a Buffer of length 10, filled with 0x1. const buf2 = Buffer.alloc(10, 1); // Creates an uninitialized buffer of length 10. // This is faster than calling Buffer.alloc() but the returned // Buffer instance might contain old data that needs to be // overwritten using either fill() or write(). const buf3 = Buffer.allocUnsafe(10); // Creates a Buffer containing [0x1, 0x2, 0x3]. const buf4 = Buffer.from([1, 2, 3]); // Creates a Buffer containing UTF-8 bytes [0x74, 0xc3, 0xa9, 0x73, 0x74]. const buf5 = Buffer.from('tést'); // Creates a Buffer containing Latin-1 bytes [0x74, 0xe9, 0x73, 0x74]. const buf6 = Buffer.from('tést', 'latin1');</code></pre> <h2><code>Buffer.from()</code>, <code>Buffer.alloc()</code>, and <code>Buffer.allocUnsafe()</code><span><a class="mark" href="#buffer_buffer_from_buffer_alloc_and_buffer_allocunsafe" id="buffer_buffer_from_buffer_alloc_and_buffer_allocunsafe">#</a></span></h2> <p>In versions of Node.js prior to 6.0.0, <code>Buffer</code> instances were created using the <code>Buffer</code> constructor function, which allocates the returned <code>Buffer</code> differently based on what arguments are provided:</p> <ul> <li>Passing a number as the first argument to <code>Buffer()</code> (e.g. <code>new Buffer(10)</code>) allocates a new <code>Buffer</code> object of the specified size. Prior to Node.js 8.0.0, the memory allocated for such <code>Buffer</code> instances is <em>not</em> initialized and <em>can contain sensitive data</em>. Such <code>Buffer</code> instances <em>must</em> be subsequently initialized by using either <a href="#buffer_buf_fill_value_offset_end_encoding"><code>buf.fill(0)</code></a> or by writing to the entire <code>Buffer</code>. While this behavior is <em>intentional</em> to improve performance, development experience has demonstrated that a more explicit distinction is required between creating a fast-but-uninitialized <code>Buffer</code> versus creating a slower-but-safer <code>Buffer</code>. Starting in Node.js 8.0.0, <code>Buffer(num)</code> and <code>new Buffer(num)</code> will return a <code>Buffer</code> with initialized memory.</li> <li>Passing a string, array, or <code>Buffer</code> as the first argument copies the passed object's data into the <code>Buffer</code>.</li> <li>Passing an <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer"><code>ArrayBuffer</code></a> or a <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer"><code>SharedArrayBuffer</code></a> returns a <code>Buffer</code> that shares allocated memory with the given array buffer.</li> </ul> <p>Because the behavior of <code>new Buffer()</code> is different depending on the type of the first argument, security and reliability issues can be inadvertently introduced into applications when argument validation or <code>Buffer</code> initialization is not performed.</p> <p>To make the creation of <code>Buffer</code> instances more reliable and less error-prone, the various forms of the <code>new Buffer()</code> constructor have been <strong>deprecated</strong> and replaced by separate <code>Buffer.from()</code>, <a href="#buffer_class_method_buffer_alloc_size_fill_encoding"><code>Buffer.alloc()</code></a>, and <a href="#buffer_class_method_buffer_allocunsafe_size"><code>Buffer.allocUnsafe()</code></a> methods.</p> <p><em>Developers should migrate all existing uses of the <code>new Buffer()</code> constructors to one of these new APIs.</em></p> <ul> <li><a href="#buffer_class_method_buffer_from_array"><code>Buffer.from(array)</code></a> returns a new <code>Buffer</code> that <em>contains a copy</em> of the provided octets.</li> <li><a href="#buffer_class_method_buffer_from_arraybuffer_byteoffset_length"><code>Buffer.from(arrayBuffer[, byteOffset[, length]])</code></a> returns a new <code>Buffer</code> that <em>shares the same allocated memory</em> as the given <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer"><code>ArrayBuffer</code></a>.</li> <li><a href="#buffer_class_method_buffer_from_buffer"><code>Buffer.from(buffer)</code></a> returns a new <code>Buffer</code> that <em>contains a copy</em> of the contents of the given <code>Buffer</code>.</li> <li><a href="#buffer_class_method_buffer_from_string_encoding"><code>Buffer.from(string[, encoding])</code></a> returns a new <code>Buffer</code> that <em>contains a copy</em> of the provided string.</li> <li><a href="#buffer_class_method_buffer_alloc_size_fill_encoding"><code>Buffer.alloc(size[, fill[, encoding]])</code></a> returns a new initialized <code>Buffer</code> of the specified size. This method is slower than <a href="#buffer_class_method_buffer_allocunsafe_size"><code>Buffer.allocUnsafe(size)</code></a> but guarantees that newly created <code>Buffer</code> instances never contain old data that is potentially sensitive.</li> <li><a href="#buffer_class_method_buffer_allocunsafe_size"><code>Buffer.allocUnsafe(size)</code></a> and <a href="#buffer_class_method_buffer_allocunsafeslow_size"><code>Buffer.allocUnsafeSlow(size)</code></a> each return a new uninitialized <code>Buffer</code> of the specified <code>size</code>. Because the <code>Buffer</code> is uninitialized, the allocated segment of memory might contain old data that is potentially sensitive.</li> </ul> <p><code>Buffer</code> instances returned by <a href="#buffer_class_method_buffer_allocunsafe_size"><code>Buffer.allocUnsafe()</code></a> <em>may</em> be allocated off a shared internal memory pool if <code>size</code> is less than or equal to half <a href="#buffer_class_property_buffer_poolsize"><code>Buffer.poolSize</code></a>. Instances returned by <a href="#buffer_class_method_buffer_allocunsafeslow_size"><code>Buffer.allocUnsafeSlow()</code></a> <em>never</em> use the shared internal memory pool.</p> <h3>The <code>--zero-fill-buffers</code> command line option<span><a class="mark" href="#buffer_the_zero_fill_buffers_command_line_option" id="buffer_the_zero_fill_buffers_command_line_option">#</a></span></h3> <div class="api_metadata"> <span>Added in: v5.10.0</span> </div><p>Node.js can be started using the <code>--zero-fill-buffers</code> command line option to cause all newly allocated <code>Buffer</code> instances to be zero-filled upon creation by default, including buffers returned by <code>new Buffer(size)</code>, <a href="#buffer_class_method_buffer_allocunsafe_size"><code>Buffer.allocUnsafe()</code></a>, <a href="#buffer_class_method_buffer_allocunsafeslow_size"><code>Buffer.allocUnsafeSlow()</code></a>, and <code>new SlowBuffer(size)</code>. Use of this flag can have a significant negative impact on performance. Use of the <code>--zero-fill-buffers</code> option is recommended only when necessary to enforce that newly allocated <code>Buffer</code> instances cannot contain old data that is potentially sensitive.</p> <pre><code class="language-txt">$ node --zero-fill-buffers > Buffer.allocUnsafe(5); <Buffer 00 00 00 00 00></code></pre> <h3>What makes <code>Buffer.allocUnsafe()</code> and <code>Buffer.allocUnsafeSlow()</code> "unsafe"?<span><a class="mark" href="#buffer_what_makes_buffer_allocunsafe_and_buffer_allocunsafeslow_unsafe" id="buffer_what_makes_buffer_allocunsafe_and_buffer_allocunsafeslow_unsafe">#</a></span></h3> <p>When calling <a href="#buffer_class_method_buffer_allocunsafe_size"><code>Buffer.allocUnsafe()</code></a> and <a href="#buffer_class_method_buffer_allocunsafeslow_size"><code>Buffer.allocUnsafeSlow()</code></a>, the segment of allocated memory is <em>uninitialized</em> (it is not zeroed-out). While this design makes the allocation of memory quite fast, the allocated segment of memory might contain old data that is potentially sensitive. Using a <code>Buffer</code> created by <a href="#buffer_class_method_buffer_allocunsafe_size"><code>Buffer.allocUnsafe()</code></a> without <em>completely</em> overwriting the memory can allow this old data to be leaked when the <code>Buffer</code> memory is read.</p> <p>While there are clear performance advantages to using <a href="#buffer_class_method_buffer_allocunsafe_size"><code>Buffer.allocUnsafe()</code></a>, extra care <em>must</em> be taken in order to avoid introducing security vulnerabilities into an application.</p> <h2>Buffers and Character Encodings<span><a class="mark" href="#buffer_buffers_and_character_encodings" id="buffer_buffers_and_character_encodings">#</a></span></h2> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v6.4.0</td> <td><p>Introduced <code>latin1</code> as an alias for <code>binary</code>.</p> </td></tr> <tr><td>v5.0.0</td> <td><p>Removed the deprecated <code>raw</code> and <code>raws</code> encodings.</p> </td></tr> </table> </details> </div><p>When string data is stored in or extracted out of a <code>Buffer</code> instance, a character encoding may be specified.</p> <pre><code class="language-js">const buf = Buffer.from('hello world', 'ascii'); console.log(buf.toString('hex')); // Prints: 68656c6c6f20776f726c64 console.log(buf.toString('base64')); // Prints: aGVsbG8gd29ybGQ= console.log(Buffer.from('fhqwhgads', 'ascii')); // Prints: <Buffer 66 68 71 77 68 67 61 64 73> console.log(Buffer.from('fhqwhgads', 'utf16le')); // Prints: <Buffer 66 00 68 00 71 00 77 00 68 00 67 00 61 00 64 00 73 00></code></pre> <p>The character encodings currently supported by Node.js include:</p> <ul> <li><p><code>'ascii'</code> - For 7-bit ASCII data only. This encoding is fast and will strip the high bit if set.</p> </li> <li><p><code>'utf8'</code> - Multibyte encoded Unicode characters. Many web pages and other document formats use UTF-8.</p> </li> <li><p><code>'utf16le'</code> - 2 or 4 bytes, little-endian encoded Unicode characters. Surrogate pairs (U+10000 to U+10FFFF) are supported.</p> </li> <li><p><code>'ucs2'</code> - Alias of <code>'utf16le'</code>.</p> </li> <li><p><code>'base64'</code> - Base64 encoding. When creating a <code>Buffer</code> from a string, this encoding will also correctly accept "URL and Filename Safe Alphabet" as specified in <a href="https://tools.ietf.org/html/rfc4648#section-5">RFC4648, Section 5</a>.</p> </li> <li><p><code>'latin1'</code> - A way of encoding the <code>Buffer</code> into a one-byte encoded string (as defined by the IANA in <a href="https://tools.ietf.org/html/rfc1345">RFC1345</a>, page 63, to be the Latin-1 supplement block and C0/C1 control codes).</p> </li> <li><p><code>'binary'</code> - Alias for <code>'latin1'</code>.</p> </li> <li><p><code>'hex'</code> - Encode each byte as two hexadecimal characters.</p> </li> </ul> <p>Modern Web browsers follow the <a href="https://encoding.spec.whatwg.org/">WHATWG Encoding Standard</a> which aliases both <code>'latin1'</code> and <code>'ISO-8859-1'</code> to <code>'win-1252'</code>. This means that while doing something like <code>http.get()</code>, if the returned charset is one of those listed in the WHATWG specification it is possible that the server actually returned <code>'win-1252'</code>-encoded data, and using <code>'latin1'</code> encoding may incorrectly decode the characters.</p> <h2>Buffers and TypedArray<span><a class="mark" href="#buffer_buffers_and_typedarray" id="buffer_buffers_and_typedarray">#</a></span></h2> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v3.0.0</td> <td><p>The <code>Buffer</code>s class now inherits from <code>Uint8Array</code>.</p> </td></tr> </table> </details> </div><p><code>Buffer</code> instances are also <a href="#buffer_buf_slice_start_end"><code>Uint8Array</code>] instances. However, there are subtle incompatibilities with <a href="#buffer_buf_slice_start_end"><code>TypedArray</code>]. For example, while <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer/slice"><code>ArrayBuffer#slice()</code></a> creates a copy of the slice, the implementation of [<code>Buffer#slice()</code></a> creates a view over the existing <code>Buffer</code> without copying, making [<code>Buffer#slice()</code></a> far more efficient.</p> <p>It is also possible to create new <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a> instances from a <code>Buffer</code> with the following caveats:</p> <ol> <li><p>The <code>Buffer</code> object's memory is copied to the <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a>, not shared.</p> </li> <li><p>The <code>Buffer</code> object's memory is interpreted as an array of distinct elements, and not as a byte array of the target type. That is, <code>new Uint32Array(Buffer.from([1, 2, 3, 4]))</code> creates a 4-element <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint32Array"><code>Uint32Array</code></a> with elements <code>[1, 2, 3, 4]</code>, not a <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint32Array"><code>Uint32Array</code></a> with a single element <code>[0x1020304]</code> or <code>[0x4030201]</code>.</p> </li> </ol> <p>It is possible to create a new <code>Buffer</code> that shares the same allocated memory as a <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a> instance by using the <code>TypedArray</code> object's <code>.buffer</code> property.</p> <pre><code class="language-js">const arr = new Uint16Array(2); arr[0] = 5000; arr[1] = 4000; // Copies the contents of `arr` const buf1 = Buffer.from(arr); // Shares memory with `arr` const buf2 = Buffer.from(arr.buffer); console.log(buf1); // Prints: <Buffer 88 a0> console.log(buf2); // Prints: <Buffer 88 13 a0 0f> arr[1] = 6000; console.log(buf1); // Prints: <Buffer 88 a0> console.log(buf2); // Prints: <Buffer 88 13 70 17></code></pre> <p>Note that when creating a <code>Buffer</code> using a <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a>'s <code>.buffer</code>, it is possible to use only a portion of the underlying <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer"><code>ArrayBuffer</code></a> by passing in <code>byteOffset</code> and <code>length</code> parameters.</p> <pre><code class="language-js">const arr = new Uint16Array(20); const buf = Buffer.from(arr.buffer, 0, 16); console.log(buf.length); // Prints: 16</code></pre> <p>The <code>Buffer.from()</code> and <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray/from"><code>TypedArray.from()</code></a> have different signatures and implementations. Specifically, the <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a> variants accept a second argument that is a mapping function that is invoked on every element of the typed array:</p> <ul> <li><code>TypedArray.from(source[, mapFn[, thisArg]])</code></li> </ul> <p>The <code>Buffer.from()</code> method, however, does not support the use of a mapping function:</p> <ul> <li><a href="#buffer_class_method_buffer_from_array"><code>Buffer.from(array)</code></a></li> <li><a href="#buffer_class_method_buffer_from_buffer"><code>Buffer.from(buffer)</code></a></li> <li><a href="#buffer_class_method_buffer_from_arraybuffer_byteoffset_length"><code>Buffer.from(arrayBuffer[, byteOffset[, length]])</code></a></li> <li><a href="#buffer_class_method_buffer_from_string_encoding"><code>Buffer.from(string[, encoding])</code></a></li> </ul> <h2>Buffers and iteration<span><a class="mark" href="#buffer_buffers_and_iteration" id="buffer_buffers_and_iteration">#</a></span></h2> <p><code>Buffer</code> instances can be iterated over using <code>for..of</code> syntax:</p> <pre><code class="language-js">const buf = Buffer.from([1, 2, 3]); // Prints: // 1 // 2 // 3 for (const b of buf) { console.log(b); }</code></pre> <p>Additionally, the <a href="#buffer_buf_values"><code>buf.values()</code></a>, <a href="#buffer_buf_keys"><code>buf.keys()</code></a>, and <a href="#buffer_buf_entries"><code>buf.entries()</code></a> methods can be used to create iterators.</p> <h2>Class: Buffer<span><a class="mark" href="#buffer_class_buffer" id="buffer_class_buffer">#</a></span></h2> <p>The <code>Buffer</code> class is a global type for dealing with binary data directly. It can be constructed in a variety of ways.</p> <h3>new Buffer(array)<span><a class="mark" href="#buffer_new_buffer_array" id="buffer_new_buffer_array">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v10.0.0</td> <td><p>Calling this constructor emits a deprecation warning when run from code outside the <code>node_modules</code> directory.</p> </td></tr> <tr><td>v7.2.1</td> <td><p>Calling this constructor no longer emits a deprecation warning.</p> </td></tr> <tr><td>v7.0.0</td> <td><p>Calling this constructor emits a deprecation warning now.</p> </td></tr> <tr><td>v6.0.0</td> <td><p><span>Deprecated since: v6.0.0</span></p> </td></tr> </table> </details> </div><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use [`Buffer.from(array)`] instead.</div><ul> <li><code>array</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer[]></a> An array of bytes to copy from.</li> </ul> <p>Allocates a new <code>Buffer</code> using an <code>array</code> of octets.</p> <pre><code class="language-js">// Creates a new Buffer containing the UTF-8 bytes of the string 'buffer' const buf = new Buffer([0x62, 0x75, 0x66, 0x66, 0x65, 0x72]);</code></pre> <h3>new Buffer(arrayBuffer[, byteOffset[, length]])<span><a class="mark" href="#buffer_new_buffer_arraybuffer_byteoffset_length" id="buffer_new_buffer_arraybuffer_byteoffset_length">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v10.0.0</td> <td><p>Calling this constructor emits a deprecation warning when run from code outside the <code>node_modules</code> directory.</p> </td></tr> <tr><td>v7.2.1</td> <td><p>Calling this constructor no longer emits a deprecation warning.</p> </td></tr> <tr><td>v7.0.0</td> <td><p>Calling this constructor emits a deprecation warning now.</p> </td></tr> <tr><td>v6.0.0</td> <td><p>The <code>byteOffset</code> and <code>length</code> parameters are supported now.</p> </td></tr> <tr><td>v6.0.0</td> <td><p><span>Deprecated since: v6.0.0</span></p> </td></tr> <tr><td>v3.0.0</td> <td><p><span>Added in: v3.0.0</span></p> </td></tr> </table> </details> </div><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use [`Buffer.from(arrayBuffer[, byteOffset[, length]])`][`Buffer.from(arrayBuf)`] instead.</div><ul> <li><code>arrayBuffer</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer" class="type"><ArrayBuffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer" class="type"><SharedArrayBuffer></a> An <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer"><code>ArrayBuffer</code></a>, <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer"><code>SharedArrayBuffer</code></a> or the <code>.buffer</code> property of a <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a>.</li> <li><code>byteOffset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Index of first byte to expose. <strong>Default:</strong> <code>0</code>.</li> <li><code>length</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to expose. <strong>Default:</strong> <code>arrayBuffer.length - byteOffset</code>.</li> </ul> <p>This creates a view of the <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer"><code>ArrayBuffer</code></a> or <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer"><code>SharedArrayBuffer</code></a> without copying the underlying memory. For example, when passed a reference to the <code>.buffer</code> property of a <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a> instance, the newly created <code>Buffer</code> will share the same allocated memory as the <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a>.</p> <p>The optional <code>byteOffset</code> and <code>length</code> arguments specify a memory range within the <code>arrayBuffer</code> that will be shared by the <code>Buffer</code>.</p> <pre><code class="language-js">const arr = new Uint16Array(2); arr[0] = 5000; arr[1] = 4000; // Shares memory with `arr` const buf = new Buffer(arr.buffer); console.log(buf); // Prints: <Buffer 88 13 a0 0f> // Changing the original Uint16Array changes the Buffer also arr[1] = 6000; console.log(buf); // Prints: <Buffer 88 13 70 17></code></pre> <h3>new Buffer(buffer)<span><a class="mark" href="#buffer_new_buffer_buffer" id="buffer_new_buffer_buffer">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v10.0.0</td> <td><p>Calling this constructor emits a deprecation warning when run from code outside the <code>node_modules</code> directory.</p> </td></tr> <tr><td>v7.2.1</td> <td><p>Calling this constructor no longer emits a deprecation warning.</p> </td></tr> <tr><td>v7.0.0</td> <td><p>Calling this constructor emits a deprecation warning now.</p> </td></tr> <tr><td>v6.0.0</td> <td><p><span>Deprecated since: v6.0.0</span></p> </td></tr> </table> </details> </div><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use [`Buffer.from(buffer)`] instead.</div><ul> <li><code>buffer</code> <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array" class="type"><Uint8Array></a> An existing <code>Buffer</code> or <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array"><code>Uint8Array</code></a> from which to copy data.</li> </ul> <p>Copies the passed <code>buffer</code> data onto a new <code>Buffer</code> instance.</p> <pre><code class="language-js">const buf1 = new Buffer('buffer'); const buf2 = new Buffer(buf1); buf1[0] = 0x61; console.log(buf1.toString()); // Prints: auffer console.log(buf2.toString()); // Prints: buffer</code></pre> <h3>new Buffer(size)<span><a class="mark" href="#buffer_new_buffer_size" id="buffer_new_buffer_size">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v10.0.0</td> <td><p>Calling this constructor emits a deprecation warning when run from code outside the <code>node_modules</code> directory.</p> </td></tr> <tr><td>v8.0.0</td> <td><p>The <code>new Buffer(size)</code> will return zero-filled memory by default.</p> </td></tr> <tr><td>v7.2.1</td> <td><p>Calling this constructor no longer emits a deprecation warning.</p> </td></tr> <tr><td>v7.0.0</td> <td><p>Calling this constructor emits a deprecation warning now.</p> </td></tr> <tr><td>v6.0.0</td> <td><p><span>Deprecated since: v6.0.0</span></p> </td></tr> </table> </details> </div><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use [`Buffer.alloc()`] instead (also see [`Buffer.allocUnsafe()`]).</div><ul> <li><code>size</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The desired length of the new <code>Buffer</code>.</li> </ul> <p>Allocates a new <code>Buffer</code> of <code>size</code> bytes. If <code>size</code> is larger than <a href="#buffer_buffer_constants_max_length"><code>buffer.constants.MAX_LENGTH</code></a> or smaller than 0, <a href="errors.html#ERR_INVALID_OPT_VALUE"><code>ERR_INVALID_OPT_VALUE</code></a> is thrown. A zero-length <code>Buffer</code> is created if <code>size</code> is 0.</p> <p>Prior to Node.js 8.0.0, the underlying memory for <code>Buffer</code> instances created in this way is <em>not initialized</em>. The contents of a newly created <code>Buffer</code> are unknown and <em>may contain sensitive data</em>. Use <a href="#buffer_class_method_buffer_alloc_size_fill_encoding"><code>Buffer.alloc(size)</code></a> instead to initialize a <code>Buffer</code> with zeroes.</p> <pre><code class="language-js">const buf = new Buffer(10); console.log(buf); // Prints: <Buffer 00 00 00 00 00 00 00 00 00 00></code></pre> <h3>new Buffer(string[, encoding])<span><a class="mark" href="#buffer_new_buffer_string_encoding" id="buffer_new_buffer_string_encoding">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v10.0.0</td> <td><p>Calling this constructor emits a deprecation warning when run from code outside the <code>node_modules</code> directory.</p> </td></tr> <tr><td>v7.2.1</td> <td><p>Calling this constructor no longer emits a deprecation warning.</p> </td></tr> <tr><td>v7.0.0</td> <td><p>Calling this constructor emits a deprecation warning now.</p> </td></tr> <tr><td>v6.0.0</td> <td><p><span>Deprecated since: v6.0.0</span></p> </td></tr> </table> </details> </div><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use [`Buffer.from(string[, encoding])`][`Buffer.from(string)`] instead.</div><ul> <li><code>string</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> String to encode.</li> <li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The encoding of <code>string</code>. <strong>Default:</strong> <code>'utf8'</code>.</li> </ul> <p>Creates a new <code>Buffer</code> containing <code>string</code>. The <code>encoding</code> parameter identifies the character encoding of <code>string</code>.</p> <pre><code class="language-js">const buf1 = new Buffer('this is a tést'); const buf2 = new Buffer('7468697320697320612074c3a97374', 'hex'); console.log(buf1.toString()); // Prints: this is a tést console.log(buf2.toString()); // Prints: this is a tést console.log(buf1.toString('ascii')); // Prints: this is a tC)st</code></pre> <h3>Class Method: Buffer.alloc(size[, fill[, encoding]])<span><a class="mark" href="#buffer_class_method_buffer_alloc_size_fill_encoding" id="buffer_class_method_buffer_alloc_size_fill_encoding">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v10.0.0</td> <td><p>Attempting to fill a non-zero length buffer with a zero length buffer triggers a thrown exception.</p> </td></tr> <tr><td>v10.0.0</td> <td><p>Specifying an invalid string for <code>fill</code> triggers a thrown exception.</p> </td></tr> <tr><td>v8.9.3</td> <td><p>Specifying an invalid string for <code>fill</code> now results in a zero-filled buffer.</p> </td></tr> <tr><td>v5.10.0</td> <td><p><span>Added in: v5.10.0</span></p> </td></tr> </table> </details> </div><ul> <li><code>size</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The desired length of the new <code>Buffer</code>.</li> <li><code>fill</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> A value to pre-fill the new <code>Buffer</code> with. <strong>Default:</strong> <code>0</code>.</li> <li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> If <code>fill</code> is a string, this is its encoding. <strong>Default:</strong> <code>'utf8'</code>.</li> </ul> <p>Allocates a new <code>Buffer</code> of <code>size</code> bytes. If <code>fill</code> is <code>undefined</code>, the <code>Buffer</code> will be <em>zero-filled</em>.</p> <pre><code class="language-js">const buf = Buffer.alloc(5); console.log(buf); // Prints: <Buffer 00 00 00 00 00></code></pre> <p>Allocates a new <code>Buffer</code> of <code>size</code> bytes. If <code>size</code> is larger than <a href="#buffer_buffer_constants_max_length"><code>buffer.constants.MAX_LENGTH</code></a> or smaller than 0, <a href="errors.html#ERR_INVALID_OPT_VALUE"><code>ERR_INVALID_OPT_VALUE</code></a> is thrown. A zero-length <code>Buffer</code> is created if <code>size</code> is 0.</p> <p>If <code>fill</code> is specified, the allocated <code>Buffer</code> will be initialized by calling <a href="#buffer_buf_fill_value_offset_end_encoding"><code>buf.fill(fill)</code></a>.</p> <pre><code class="language-js">const buf = Buffer.alloc(5, 'a'); console.log(buf); // Prints: <Buffer 61 61 61 61 61></code></pre> <p>If both <code>fill</code> and <code>encoding</code> are specified, the allocated <code>Buffer</code> will be initialized by calling <a href="#buffer_buf_fill_value_offset_end_encoding"><code>buf.fill(fill, encoding)</code></a>.</p> <pre><code class="language-js">const buf = Buffer.alloc(11, 'aGVsbG8gd29ybGQ=', 'base64'); console.log(buf); // Prints: <Buffer 68 65 6c 6c 6f 20 77 6f 72 6c 64></code></pre> <p>Calling <a href="#buffer_class_method_buffer_alloc_size_fill_encoding"><code>Buffer.alloc()</code></a> can be significantly slower than the alternative <a href="#buffer_class_method_buffer_allocunsafe_size"><code>Buffer.allocUnsafe()</code></a> but ensures that the newly created <code>Buffer</code> instance contents will <em>never contain sensitive data</em>.</p> <p>A <code>TypeError</code> will be thrown if <code>size</code> is not a number.</p> <h3>Class Method: Buffer.allocUnsafe(size)<span><a class="mark" href="#buffer_class_method_buffer_allocunsafe_size" id="buffer_class_method_buffer_allocunsafe_size">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v7.0.0</td> <td><p>Passing a negative <code>size</code> will now throw an error.</p> </td></tr> <tr><td>v5.10.0</td> <td><p><span>Added in: v5.10.0</span></p> </td></tr> </table> </details> </div><ul> <li><code>size</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The desired length of the new <code>Buffer</code>.</li> </ul> <p>Allocates a new <code>Buffer</code> of <code>size</code> bytes. If <code>size</code> is larger than <a href="#buffer_buffer_constants_max_length"><code>buffer.constants.MAX_LENGTH</code></a> or smaller than 0, <a href="errors.html#ERR_INVALID_OPT_VALUE"><code>ERR_INVALID_OPT_VALUE</code></a> is thrown. A zero-length <code>Buffer</code> is created if <code>size</code> is 0.</p> <p>The underlying memory for <code>Buffer</code> instances created in this way is <em>not initialized</em>. The contents of the newly created <code>Buffer</code> are unknown and <em>may contain sensitive data</em>. Use <a href="#buffer_class_method_buffer_alloc_size_fill_encoding"><code>Buffer.alloc()</code></a> instead to initialize <code>Buffer</code> instances with zeroes.</p> <pre><code class="language-js">const buf = Buffer.allocUnsafe(10); console.log(buf); // Prints: (contents may vary): <Buffer a0 8b 28 3f 01 00 00 00 50 32> buf.fill(0); console.log(buf); // Prints: <Buffer 00 00 00 00 00 00 00 00 00 00></code></pre> <p>A <code>TypeError</code> will be thrown if <code>size</code> is not a number.</p> <p>Note that the <code>Buffer</code> module pre-allocates an internal <code>Buffer</code> instance of size <a href="#buffer_class_property_buffer_poolsize"><code>Buffer.poolSize</code></a> that is used as a pool for the fast allocation of new <code>Buffer</code> instances created using <a href="#buffer_class_method_buffer_allocunsafe_size"><code>Buffer.allocUnsafe()</code></a> and the deprecated <code>new Buffer(size)</code> constructor only when <code>size</code> is less than or equal to <code>Buffer.poolSize >> 1</code> (floor of <a href="#buffer_class_property_buffer_poolsize"><code>Buffer.poolSize</code></a> divided by two).</p> <p>Use of this pre-allocated internal memory pool is a key difference between calling <code>Buffer.alloc(size, fill)</code> vs. <code>Buffer.allocUnsafe(size).fill(fill)</code>. Specifically, <code>Buffer.alloc(size, fill)</code> will <em>never</em> use the internal <code>Buffer</code> pool, while <code>Buffer.allocUnsafe(size).fill(fill)</code> <em>will</em> use the internal <code>Buffer</code> pool if <code>size</code> is less than or equal to half <a href="#buffer_class_property_buffer_poolsize"><code>Buffer.poolSize</code></a>. The difference is subtle but can be important when an application requires the additional performance that <a href="#buffer_class_method_buffer_allocunsafe_size"><code>Buffer.allocUnsafe()</code></a> provides.</p> <h3>Class Method: Buffer.allocUnsafeSlow(size)<span><a class="mark" href="#buffer_class_method_buffer_allocunsafeslow_size" id="buffer_class_method_buffer_allocunsafeslow_size">#</a></span></h3> <div class="api_metadata"> <span>Added in: v5.12.0</span> </div><ul> <li><code>size</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The desired length of the new <code>Buffer</code>.</li> </ul> <p>Allocates a new <code>Buffer</code> of <code>size</code> bytes. If <code>size</code> is larger than <a href="#buffer_buffer_constants_max_length"><code>buffer.constants.MAX_LENGTH</code></a> or smaller than 0, <a href="errors.html#ERR_INVALID_OPT_VALUE"><code>ERR_INVALID_OPT_VALUE</code></a> is thrown. A zero-length <code>Buffer</code> is created if <code>size</code> is 0.</p> <p>The underlying memory for <code>Buffer</code> instances created in this way is <em>not initialized</em>. The contents of the newly created <code>Buffer</code> are unknown and <em>may contain sensitive data</em>. Use <a href="#buffer_buf_fill_value_offset_end_encoding"><code>buf.fill(0)</code></a> to initialize such <code>Buffer</code> instances with zeroes.</p> <p>When using <a href="#buffer_class_method_buffer_allocunsafe_size"><code>Buffer.allocUnsafe()</code></a> to allocate new <code>Buffer</code> instances, allocations under 4KB are sliced from a single pre-allocated <code>Buffer</code>. This allows applications to avoid the garbage collection overhead of creating many individually allocated <code>Buffer</code> instances. This approach improves both performance and memory usage by eliminating the need to track and clean up as many persistent objects.</p> <p>However, in the case where a developer may need to retain a small chunk of memory from a pool for an indeterminate amount of time, it may be appropriate to create an un-pooled <code>Buffer</code> instance using <code>Buffer.allocUnsafeSlow()</code> and then copying out the relevant bits.</p> <pre><code class="language-js">// Need to keep around a few small chunks of memory const store = []; socket.on('readable', () => { let data; while (null !== (data = readable.read())) { // Allocate for retained data const sb = Buffer.allocUnsafeSlow(10); // Copy the data into the new allocation data.copy(sb, 0, 0, 10); store.push(sb); } });</code></pre> <p><code>Buffer.allocUnsafeSlow()</code> should be used only as a last resort after a developer has observed undue memory retention in their applications.</p> <p>A <code>TypeError</code> will be thrown if <code>size</code> is not a number.</p> <h3>Class Method: Buffer.byteLength(string[, encoding])<span><a class="mark" href="#buffer_class_method_buffer_bytelength_string_encoding" id="buffer_class_method_buffer_bytelength_string_encoding">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v7.0.0</td> <td><p>Passing invalid input will now throw an error.</p> </td></tr> <tr><td>v5.10.0</td> <td><p>The <code>string</code> parameter can now be any <code>TypedArray</code>, <code>DataView</code> or <code>ArrayBuffer</code>.</p> </td></tr> <tr><td>v0.1.90</td> <td><p><span>Added in: v0.1.90</span></p> </td></tr> </table> </details> </div><ul> <li><code>string</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray" class="type"><TypedArray></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView" class="type"><DataView></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer" class="type"><ArrayBuffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer" class="type"><SharedArrayBuffer></a> A value to calculate the length of.</li> <li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> If <code>string</code> is a string, this is its encoding. <strong>Default:</strong> <code>'utf8'</code>.</li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The number of bytes contained within <code>string</code>.</li> </ul> <p>Returns the actual byte length of a string. This is not the same as <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/length"><code>String.prototype.length</code></a> since that returns the number of <em>characters</em> in a string.</p> <p>For <code>'base64'</code> and <code>'hex'</code>, this function assumes valid input. For strings that contain non-Base64/Hex-encoded data (e.g. whitespace), the return value might be greater than the length of a <code>Buffer</code> created from the string.</p> <pre><code class="language-js">const str = '\u00bd + \u00bc = \u00be'; console.log(`${str}: ${str.length} characters, ` + `${Buffer.byteLength(str, 'utf8')} bytes`); // Prints: ½ + ¼ = ¾: 9 characters, 12 bytes</code></pre> <p>When <code>string</code> is a <code>Buffer</code>/<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView"><code>DataView</code></a>/<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a>/<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer"><code>ArrayBuffer</code></a>/ <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer"><code>SharedArrayBuffer</code></a>, the actual byte length is returned.</p> <h3>Class Method: Buffer.compare(buf1, buf2)<span><a class="mark" href="#buffer_class_method_buffer_compare_buf1_buf2" id="buffer_class_method_buffer_compare_buf1_buf2">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v8.0.0</td> <td><p>The arguments can now be <code>Uint8Array</code>s.</p> </td></tr> <tr><td>v0.11.13</td> <td><p><span>Added in: v0.11.13</span></p> </td></tr> </table> </details> </div><ul> <li><code>buf1</code> <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array" class="type"><Uint8Array></a></li> <li><code>buf2</code> <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array" class="type"><Uint8Array></a></li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> </ul> <p>Compares <code>buf1</code> to <code>buf2</code> typically for the purpose of sorting arrays of <code>Buffer</code> instances. This is equivalent to calling <a href="#buffer_buf_compare_target_targetstart_targetend_sourcestart_sourceend"><code>buf1.compare(buf2)</code></a>.</p> <pre><code class="language-js">const buf1 = Buffer.from('1234'); const buf2 = Buffer.from('0123'); const arr = [buf1, buf2]; console.log(arr.sort(Buffer.compare)); // Prints: [ <Buffer 30 31 32 33>, <Buffer 31 32 33 34> ] // (This result is equal to: [buf2, buf1])</code></pre> <h3>Class Method: Buffer.concat(list[, totalLength])<span><a class="mark" href="#buffer_class_method_buffer_concat_list_totallength" id="buffer_class_method_buffer_concat_list_totallength">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v8.0.0</td> <td><p>The elements of <code>list</code> can now be <code>Uint8Array</code>s.</p> </td></tr> <tr><td>v0.7.11</td> <td><p><span>Added in: v0.7.11</span></p> </td></tr> </table> </details> </div><ul> <li><code>list</code> <a href="buffer.html#buffer_class_buffer" class="type"><Buffer[]></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array" class="type"><Uint8Array[]></a> List of <code>Buffer</code> or <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array"><code>Uint8Array</code></a> instances to concat.</li> <li><code>totalLength</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Total length of the <code>Buffer</code> instances in <code>list</code> when concatenated.</li> <li>Returns: <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a></li> </ul> <p>Returns a new <code>Buffer</code> which is the result of concatenating all the <code>Buffer</code> instances in the <code>list</code> together.</p> <p>If the list has no items, or if the <code>totalLength</code> is 0, then a new zero-length <code>Buffer</code> is returned.</p> <p>If <code>totalLength</code> is not provided, it is calculated from the <code>Buffer</code> instances in <code>list</code>. This however causes an additional loop to be executed in order to calculate the <code>totalLength</code>, so it is faster to provide the length explicitly if it is already known.</p> <p>If <code>totalLength</code> is provided, it is coerced to an unsigned integer. If the combined length of the <code>Buffer</code>s in <code>list</code> exceeds <code>totalLength</code>, the result is truncated to <code>totalLength</code>.</p> <pre><code class="language-js">// Create a single `Buffer` from a list of three `Buffer` instances. const buf1 = Buffer.alloc(10); const buf2 = Buffer.alloc(14); const buf3 = Buffer.alloc(18); const totalLength = buf1.length + buf2.length + buf3.length; console.log(totalLength); // Prints: 42 const bufA = Buffer.concat([buf1, buf2, buf3], totalLength); console.log(bufA); // Prints: <Buffer 00 00 00 00 ...> console.log(bufA.length); // Prints: 42</code></pre> <h3>Class Method: Buffer.from(array)<span><a class="mark" href="#buffer_class_method_buffer_from_array" id="buffer_class_method_buffer_from_array">#</a></span></h3> <div class="api_metadata"> <span>Added in: v5.10.0</span> </div><ul> <li><code>array</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer[]></a></li> </ul> <p>Allocates a new <code>Buffer</code> using an <code>array</code> of octets.</p> <pre><code class="language-js">// Creates a new Buffer containing UTF-8 bytes of the string 'buffer' const buf = Buffer.from([0x62, 0x75, 0x66, 0x66, 0x65, 0x72]);</code></pre> <p>A <code>TypeError</code> will be thrown if <code>array</code> is not an <code>Array</code>.</p> <h3>Class Method: Buffer.from(arrayBuffer[, byteOffset[, length]])<span><a class="mark" href="#buffer_class_method_buffer_from_arraybuffer_byteoffset_length" id="buffer_class_method_buffer_from_arraybuffer_byteoffset_length">#</a></span></h3> <div class="api_metadata"> <span>Added in: v5.10.0</span> </div><ul> <li><code>arrayBuffer</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer" class="type"><ArrayBuffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer" class="type"><SharedArrayBuffer></a> An <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer"><code>ArrayBuffer</code></a>, <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer"><code>SharedArrayBuffer</code></a>, or the <code>.buffer</code> property of a <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a>.</li> <li><code>byteOffset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Index of first byte to expose. <strong>Default:</strong> <code>0</code>.</li> <li><code>length</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to expose. <strong>Default:</strong> <code>arrayBuffer.length - byteOffset</code>.</li> </ul> <p>This creates a view of the <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer"><code>ArrayBuffer</code></a> without copying the underlying memory. For example, when passed a reference to the <code>.buffer</code> property of a <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a> instance, the newly created <code>Buffer</code> will share the same allocated memory as the <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray"><code>TypedArray</code></a>.</p> <pre><code class="language-js">const arr = new Uint16Array(2); arr[0] = 5000; arr[1] = 4000; // Shares memory with `arr` const buf = Buffer.from(arr.buffer); console.log(buf); // Prints: <Buffer 88 13 a0 0f> // Changing the original Uint16Array changes the Buffer also arr[1] = 6000; console.log(buf); // Prints: <Buffer 88 13 70 17></code></pre> <p>The optional <code>byteOffset</code> and <code>length</code> arguments specify a memory range within the <code>arrayBuffer</code> that will be shared by the <code>Buffer</code>.</p> <pre><code class="language-js">const ab = new ArrayBuffer(10); const buf = Buffer.from(ab, 0, 2); console.log(buf.length); // Prints: 2</code></pre> <p>A <code>TypeError</code> will be thrown if <code>arrayBuffer</code> is not an <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer"><code>ArrayBuffer</code></a> or a <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer"><code>SharedArrayBuffer</code></a>.</p> <h3>Class Method: Buffer.from(buffer)<span><a class="mark" href="#buffer_class_method_buffer_from_buffer" id="buffer_class_method_buffer_from_buffer">#</a></span></h3> <div class="api_metadata"> <span>Added in: v5.10.0</span> </div><ul> <li><code>buffer</code> <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array" class="type"><Uint8Array></a> An existing <code>Buffer</code> or <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array"><code>Uint8Array</code></a> from which to copy data.</li> </ul> <p>Copies the passed <code>buffer</code> data onto a new <code>Buffer</code> instance.</p> <pre><code class="language-js">const buf1 = Buffer.from('buffer'); const buf2 = Buffer.from(buf1); buf1[0] = 0x61; console.log(buf1.toString()); // Prints: auffer console.log(buf2.toString()); // Prints: buffer</code></pre> <p>A <code>TypeError</code> will be thrown if <code>buffer</code> is not a <code>Buffer</code>.</p> <h3>Class Method: Buffer.from(object[, offsetOrEncoding[, length]])<span><a class="mark" href="#buffer_class_method_buffer_from_object_offsetorencoding_length" id="buffer_class_method_buffer_from_object_offsetorencoding_length">#</a></span></h3> <div class="api_metadata"> <span>Added in: v8.2.0</span> </div><ul> <li><code>object</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a> An object supporting <code>Symbol.toPrimitive</code> or <code>valueOf()</code></li> <li><code>offsetOrEncoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> A byte-offset or encoding, depending on the value returned either by <code>object.valueOf()</code> or <code>object[Symbol.toPrimitive]()</code>.</li> <li><code>length</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> A length, depending on the value returned either by <code>object.valueOf()</code> or <code>object[Symbol.toPrimitive]()</code>.</li> </ul> <p>For objects whose <code>valueOf()</code> function returns a value not strictly equal to <code>object</code>, returns <code>Buffer.from(object.valueOf(), offsetOrEncoding, length)</code>.</p> <pre><code class="language-js">const buf = Buffer.from(new String('this is a test')); // Prints: <Buffer 74 68 69 73 20 69 73 20 61 20 74 65 73 74></code></pre> <p>For objects that support <code>Symbol.toPrimitive</code>, returns <code>Buffer.from(object[Symbol.toPrimitive](), offsetOrEncoding, length)</code>.</p> <pre><code class="language-js">class Foo { [Symbol.toPrimitive]() { return 'this is a test'; } } const buf = Buffer.from(new Foo(), 'utf8'); // Prints: <Buffer 74 68 69 73 20 69 73 20 61 20 74 65 73 74></code></pre> <h3>Class Method: Buffer.from(string[, encoding])<span><a class="mark" href="#buffer_class_method_buffer_from_string_encoding" id="buffer_class_method_buffer_from_string_encoding">#</a></span></h3> <div class="api_metadata"> <span>Added in: v5.10.0</span> </div><ul> <li><code>string</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> A string to encode.</li> <li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The encoding of <code>string</code>. <strong>Default:</strong> <code>'utf8'</code>.</li> </ul> <p>Creates a new <code>Buffer</code> containing <code>string</code>. The <code>encoding</code> parameter identifies the character encoding of <code>string</code>.</p> <pre><code class="language-js">const buf1 = Buffer.from('this is a tést'); const buf2 = Buffer.from('7468697320697320612074c3a97374', 'hex'); console.log(buf1.toString()); // Prints: this is a tést console.log(buf2.toString()); // Prints: this is a tést console.log(buf1.toString('ascii')); // Prints: this is a tC)st</code></pre> <p>A <code>TypeError</code> will be thrown if <code>string</code> is not a string.</p> <h3>Class Method: Buffer.isBuffer(obj)<span><a class="mark" href="#buffer_class_method_buffer_isbuffer_obj" id="buffer_class_method_buffer_isbuffer_obj">#</a></span></h3> <div class="api_metadata"> <span>Added in: v0.1.101</span> </div><ul> <li><code>obj</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> </ul> <p>Returns <code>true</code> if <code>obj</code> is a <code>Buffer</code>, <code>false</code> otherwise.</p> <h3>Class Method: Buffer.isEncoding(encoding)<span><a class="mark" href="#buffer_class_method_buffer_isencoding_encoding" id="buffer_class_method_buffer_isencoding_encoding">#</a></span></h3> <div class="api_metadata"> <span>Added in: v0.9.1</span> </div><ul> <li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> A character encoding name to check.</li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> </ul> <p>Returns <code>true</code> if <code>encoding</code> contains a supported character encoding, or <code>false</code> otherwise.</p> <h3>Class Property: Buffer.poolSize<span><a class="mark" href="#buffer_class_property_buffer_poolsize" id="buffer_class_property_buffer_poolsize">#</a></span></h3> <div class="api_metadata"> <span>Added in: v0.11.3</span> </div><ul> <li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> <strong>Default:</strong> <code>8192</code></li> </ul> <p>This is the size (in bytes) of pre-allocated internal <code>Buffer</code> instances used for pooling. This value may be modified.</p> <h3>buf[index]<span><a class="mark" href="#buffer_buf_index" id="buffer_buf_index">#</a></span></h3> <div class="api_metadata"> </div><p>The index operator <code>[index]</code> can be used to get and set the octet at position <code>index</code> in <code>buf</code>. The values refer to individual bytes, so the legal value range is between <code>0x00</code> and <code>0xFF</code> (hex) or <code>0</code> and <code>255</code> (decimal).</p> <p>This operator is inherited from <code>Uint8Array</code>, so its behavior on out-of-bounds access is the same as <code>UInt8Array</code> - that is, getting returns <code>undefined</code> and setting does nothing.</p> <pre><code class="language-js">// Copy an ASCII string into a `Buffer` one byte at a time. const str = 'Node.js'; const buf = Buffer.allocUnsafe(str.length); for (let i = 0; i < str.length; i++) { buf[i] = str.charCodeAt(i); } console.log(buf.toString('ascii')); // Prints: Node.js</code></pre> <h3>buf.buffer<span><a class="mark" href="#buffer_buf_buffer" id="buffer_buf_buffer">#</a></span></h3> <ul> <li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer" class="type"><ArrayBuffer></a> The underlying <code>ArrayBuffer</code> object based on which this <code>Buffer</code> object is created.</li> </ul> <pre><code class="language-js">const arrayBuffer = new ArrayBuffer(16); const buffer = Buffer.from(arrayBuffer); console.log(buffer.buffer === arrayBuffer); // Prints: true</code></pre> <h3>buf.byteOffset<span><a class="mark" href="#buffer_buf_byteoffset" id="buffer_buf_byteoffset">#</a></span></h3> <ul> <li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The <code>byteOffset</code> on the underlying <code>ArrayBuffer</code> object based on which this <code>Buffer</code> object is created.</li> </ul> <p>When setting <code>byteOffset</code> in <code>Buffer.from(ArrayBuffer, byteOffset, length)</code> or sometimes when allocating a buffer smaller than <code>Buffer.poolSize</code> the buffer doesn't start from a zero offset on the underlying <code>ArrayBuffer</code>.</p> <p>This can cause problems when accessing the underlying <code>ArrayBuffer</code> directly using <code>buf.buffer</code>, as the first bytes in this <code>ArrayBuffer</code> may be unrelated to the <code>buf</code> object itself.</p> <p>A common issue is when casting a <code>Buffer</code> object to a <code>TypedArray</code> object, in this case one needs to specify the <code>byteOffset</code> correctly:</p> <pre><code class="language-js">// Create a buffer smaller than `Buffer.poolSize`. const nodeBuffer = new Buffer.from([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]); // When casting the Node.js Buffer to an Int8 TypedArray remember to use the // byteOffset. new Int8Array(nodeBuffer.buffer, nodeBuffer.byteOffset, nodeBuffer.length);</code></pre> <h3>buf.compare(target[, targetStart[, targetEnd[, sourceStart[, sourceEnd]]]])<span><a class="mark" href="#buffer_buf_compare_target_targetstart_targetend_sourcestart_sourceend" id="buffer_buf_compare_target_targetstart_targetend_sourcestart_sourceend">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v8.0.0</td> <td><p>The <code>target</code> parameter can now be a <code>Uint8Array</code>.</p> </td></tr> <tr><td>v5.11.0</td> <td><p>Additional parameters for specifying offsets are supported now.</p> </td></tr> <tr><td>v0.11.13</td> <td><p><span>Added in: v0.11.13</span></p> </td></tr> </table> </details> </div><ul> <li><code>target</code> <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array" class="type"><Uint8Array></a> A <code>Buffer</code> or <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array"><code>Uint8Array</code></a> with which to compare <code>buf</code>.</li> <li><code>targetStart</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The offset within <code>target</code> at which to begin comparison. <strong>Default:</strong> <code>0</code>.</li> <li><code>targetEnd</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The offset with <code>target</code> at which to end comparison (not inclusive). <strong>Default:</strong> <code>target.length</code>.</li> <li><code>sourceStart</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The offset within <code>buf</code> at which to begin comparison. <strong>Default:</strong> <code>0</code>.</li> <li><code>sourceEnd</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The offset within <code>buf</code> at which to end comparison (not inclusive). <strong>Default:</strong> <a href="#buffer_buf_length"><code>buf.length</code></a>.</li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> </ul> <p>Compares <code>buf</code> with <code>target</code> and returns a number indicating whether <code>buf</code> comes before, after, or is the same as <code>target</code> in sort order. Comparison is based on the actual sequence of bytes in each <code>Buffer</code>.</p> <ul> <li><code>0</code> is returned if <code>target</code> is the same as <code>buf</code></li> <li><code>1</code> is returned if <code>target</code> should come <em>before</em> <code>buf</code> when sorted.</li> <li><code>-1</code> is returned if <code>target</code> should come <em>after</em> <code>buf</code> when sorted.</li> </ul> <pre><code class="language-js">const buf1 = Buffer.from('ABC'); const buf2 = Buffer.from('BCD'); const buf3 = Buffer.from('ABCD'); console.log(buf1.compare(buf1)); // Prints: 0 console.log(buf1.compare(buf2)); // Prints: -1 console.log(buf1.compare(buf3)); // Prints: -1 console.log(buf2.compare(buf1)); // Prints: 1 console.log(buf2.compare(buf3)); // Prints: 1 console.log([buf1, buf2, buf3].sort(Buffer.compare)); // Prints: [ <Buffer 41 42 43>, <Buffer 41 42 43 44>, <Buffer 42 43 44> ] // (This result is equal to: [buf1, buf3, buf2])</code></pre> <p>The optional <code>targetStart</code>, <code>targetEnd</code>, <code>sourceStart</code>, and <code>sourceEnd</code> arguments can be used to limit the comparison to specific ranges within <code>target</code> and <code>buf</code> respectively.</p> <pre><code class="language-js">const buf1 = Buffer.from([1, 2, 3, 4, 5, 6, 7, 8, 9]); const buf2 = Buffer.from([5, 6, 7, 8, 9, 1, 2, 3, 4]); console.log(buf1.compare(buf2, 5, 9, 0, 4)); // Prints: 0 console.log(buf1.compare(buf2, 0, 6, 4)); // Prints: -1 console.log(buf1.compare(buf2, 5, 6, 5)); // Prints: 1</code></pre> <p><a href="errors.html#ERR_INDEX_OUT_OF_RANGE"><code>ERR_INDEX_OUT_OF_RANGE</code></a> is thrown if <code>targetStart < 0</code>, <code>sourceStart < 0</code>, <code>targetEnd > target.byteLength</code>, or <code>sourceEnd > source.byteLength</code>.</p> <h3>buf.copy(target[, targetStart[, sourceStart[, sourceEnd]]])<span><a class="mark" href="#buffer_buf_copy_target_targetstart_sourcestart_sourceend" id="buffer_buf_copy_target_targetstart_sourcestart_sourceend">#</a></span></h3> <div class="api_metadata"> <span>Added in: v0.1.90</span> </div><ul> <li><code>target</code> <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array" class="type"><Uint8Array></a> A <code>Buffer</code> or <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array"><code>Uint8Array</code></a> to copy into.</li> <li><code>targetStart</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The offset within <code>target</code> at which to begin writing. <strong>Default:</strong> <code>0</code>.</li> <li><code>sourceStart</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The offset within <code>buf</code> from which to begin copying. <strong>Default:</strong> <code>0</code>.</li> <li><code>sourceEnd</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The offset within <code>buf</code> at which to stop copying (not inclusive). <strong>Default:</strong> <a href="#buffer_buf_length"><code>buf.length</code></a>.</li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The number of bytes copied.</li> </ul> <p>Copies data from a region of <code>buf</code> to a region in <code>target</code> even if the <code>target</code> memory region overlaps with <code>buf</code>.</p> <pre><code class="language-js">// Create two `Buffer` instances. const buf1 = Buffer.allocUnsafe(26); const buf2 = Buffer.allocUnsafe(26).fill('!'); for (let i = 0; i < 26; i++) { // 97 is the decimal ASCII value for 'a' buf1[i] = i + 97; } // Copy `buf1` bytes 16 through 19 into `buf2` starting at byte 8 of `buf2` buf1.copy(buf2, 8, 16, 20); console.log(buf2.toString('ascii', 0, 25)); // Prints: !!!!!!!!qrst!!!!!!!!!!!!!</code></pre> <pre><code class="language-js">// Create a `Buffer` and copy data from one region to an overlapping region // within the same `Buffer`. const buf = Buffer.allocUnsafe(26); for (let i = 0; i < 26; i++) { // 97 is the decimal ASCII value for 'a' buf[i] = i + 97; } buf.copy(buf, 0, 4, 10); console.log(buf.toString()); // Prints: efghijghijklmnopqrstuvwxyz</code></pre> <h3>buf.entries()<span><a class="mark" href="#buffer_buf_entries" id="buffer_buf_entries">#</a></span></h3> <div class="api_metadata"> <span>Added in: v1.1.0</span> </div><ul> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#The_iterator_protocol" class="type"><Iterator></a></li> </ul> <p>Creates and returns an <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols">iterator</a> of <code>[index, byte]</code> pairs from the contents of <code>buf</code>.</p> <pre><code class="language-js">// Log the entire contents of a `Buffer`. const buf = Buffer.from('buffer'); for (const pair of buf.entries()) { console.log(pair); } // Prints: // [0, 98] // [1, 117] // [2, 102] // [3, 102] // [4, 101] // [5, 114]</code></pre> <h3>buf.equals(otherBuffer)<span><a class="mark" href="#buffer_buf_equals_otherbuffer" id="buffer_buf_equals_otherbuffer">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v8.0.0</td> <td><p>The arguments can now be <code>Uint8Array</code>s.</p> </td></tr> <tr><td>v0.11.13</td> <td><p><span>Added in: v0.11.13</span></p> </td></tr> </table> </details> </div><ul> <li><code>otherBuffer</code> <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> A <code>Buffer</code> or <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array"><code>Uint8Array</code></a> with which to compare <code>buf</code>.</li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a></li> </ul> <p>Returns <code>true</code> if both <code>buf</code> and <code>otherBuffer</code> have exactly the same bytes, <code>false</code> otherwise.</p> <pre><code class="language-js">const buf1 = Buffer.from('ABC'); const buf2 = Buffer.from('414243', 'hex'); const buf3 = Buffer.from('ABCD'); console.log(buf1.equals(buf2)); // Prints: true console.log(buf1.equals(buf3)); // Prints: false</code></pre> <h3>buf.fill(value[, offset[, end]][, encoding])<span><a class="mark" href="#buffer_buf_fill_value_offset_end_encoding" id="buffer_buf_fill_value_offset_end_encoding">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v10.0.0</td> <td><p>Negative <code>end</code> values throw an <code>ERR_INDEX_OUT_OF_RANGE</code> error.</p> </td></tr> <tr><td>v10.0.0</td> <td><p>Attempting to fill a non-zero length buffer with a zero length buffer triggers a thrown exception.</p> </td></tr> <tr><td>v10.0.0</td> <td><p>Specifying an invalid string for <code>value</code> triggers a thrown exception.</p> </td></tr> <tr><td>v5.7.0</td> <td><p>The <code>encoding</code> parameter is supported now.</p> </td></tr> <tr><td>v0.5.0</td> <td><p><span>Added in: v0.5.0</span></p> </td></tr> </table> </details> </div><ul> <li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The value with which to fill <code>buf</code>.</li> <li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to fill <code>buf</code>. <strong>Default:</strong> <code>0</code>.</li> <li><code>end</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Where to stop filling <code>buf</code> (not inclusive). <strong>Default:</strong> <a href="#buffer_buf_length"><code>buf.length</code></a>.</li> <li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The encoding for <code>value</code> if <code>value</code> is a string. <strong>Default:</strong> <code>'utf8'</code>.</li> <li>Returns: <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> A reference to <code>buf</code>.</li> </ul> <p>Fills <code>buf</code> with the specified <code>value</code>. If the <code>offset</code> and <code>end</code> are not given, the entire <code>buf</code> will be filled:</p> <pre><code class="language-js">// Fill a `Buffer` with the ASCII character 'h'. const b = Buffer.allocUnsafe(50).fill('h'); console.log(b.toString()); // Prints: hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh</code></pre> <p><code>value</code> is coerced to a <code>uint32</code> value if it is not a string, <code>Buffer</code>, or integer. If the resulting integer is greater than <code>255</code> (decimal), <code>buf</code> will be filled with <code>value & 255</code>.</p> <p>If the final write of a <code>fill()</code> operation falls on a multi-byte character, then only the bytes of that character that fit into <code>buf</code> are written:</p> <pre><code class="language-js">// Fill a `Buffer` with a two-byte character. console.log(Buffer.allocUnsafe(3).fill('\u0222')); // Prints: <Buffer c8 a2 c8></code></pre> <p>If <code>value</code> contains invalid characters, it is truncated; if no valid fill data remains, an exception is thrown:</p> <pre><code class="language-js">const buf = Buffer.allocUnsafe(5); console.log(buf.fill('a')); // Prints: <Buffer 61 61 61 61 61> console.log(buf.fill('aazz', 'hex')); // Prints: <Buffer aa aa aa aa aa> console.log(buf.fill('zz', 'hex')); // Throws an exception.</code></pre> <h3>buf.includes(value[, byteOffset][, encoding])<span><a class="mark" href="#buffer_buf_includes_value_byteoffset_encoding" id="buffer_buf_includes_value_byteoffset_encoding">#</a></span></h3> <div class="api_metadata"> <span>Added in: v5.3.0</span> </div><ul> <li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> What to search for.</li> <li><code>byteOffset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Where to begin searching in <code>buf</code>. <strong>Default:</strong> <code>0</code>.</li> <li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> If <code>value</code> is a string, this is its encoding. <strong>Default:</strong> <code>'utf8'</code>.</li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type" class="type"><boolean></a> <code>true</code> if <code>value</code> was found in <code>buf</code>, <code>false</code> otherwise.</li> </ul> <p>Equivalent to <a href="#buffer_buf_indexof_value_byteoffset_encoding"><code>buf.indexOf() !== -1</code></a>.</p> <pre><code class="language-js">const buf = Buffer.from('this is a buffer'); console.log(buf.includes('this')); // Prints: true console.log(buf.includes('is')); // Prints: true console.log(buf.includes(Buffer.from('a buffer'))); // Prints: true console.log(buf.includes(97)); // Prints: true (97 is the decimal ASCII value for 'a') console.log(buf.includes(Buffer.from('a buffer example'))); // Prints: false console.log(buf.includes(Buffer.from('a buffer example').slice(0, 8))); // Prints: true console.log(buf.includes('this', 4)); // Prints: false</code></pre> <h3>buf.indexOf(value[, byteOffset][, encoding])<span><a class="mark" href="#buffer_buf_indexof_value_byteoffset_encoding" id="buffer_buf_indexof_value_byteoffset_encoding">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v8.0.0</td> <td><p>The <code>value</code> can now be a <code>Uint8Array</code>.</p> </td></tr> <tr><td>v5.7.0, v4.4.0</td> <td><p>When <code>encoding</code> is being passed, the <code>byteOffset</code> parameter is no longer required.</p> </td></tr> <tr><td>v1.5.0</td> <td><p><span>Added in: v1.5.0</span></p> </td></tr> </table> </details> </div><ul> <li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array" class="type"><Uint8Array></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> What to search for.</li> <li><code>byteOffset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Where to begin searching in <code>buf</code>. <strong>Default:</strong> <code>0</code>.</li> <li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> If <code>value</code> is a string, this is the encoding used to determine the binary representation of the string that will be searched for in <code>buf</code>. <strong>Default:</strong> <code>'utf8'</code>.</li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The index of the first occurrence of <code>value</code> in <code>buf</code>, or <code>-1</code> if <code>buf</code> does not contain <code>value</code>.</li> </ul> <p>If <code>value</code> is:</p> <ul> <li>a string, <code>value</code> is interpreted according to the character encoding in <code>encoding</code>.</li> <li>a <code>Buffer</code> or <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array"><code>Uint8Array</code></a>, <code>value</code> will be used in its entirety. To compare a partial <code>Buffer</code>, use <a href="#buffer_buf_slice_start_end"><code>buf.slice()</code></a>.</li> <li>a number, <code>value</code> will be interpreted as an unsigned 8-bit integer value between <code>0</code> and <code>255</code>.</li> </ul> <pre><code class="language-js">const buf = Buffer.from('this is a buffer'); console.log(buf.indexOf('this')); // Prints: 0 console.log(buf.indexOf('is')); // Prints: 2 console.log(buf.indexOf(Buffer.from('a buffer'))); // Prints: 8 console.log(buf.indexOf(97)); // Prints: 8 (97 is the decimal ASCII value for 'a') console.log(buf.indexOf(Buffer.from('a buffer example'))); // Prints: -1 console.log(buf.indexOf(Buffer.from('a buffer example').slice(0, 8))); // Prints: 8 const utf16Buffer = Buffer.from('\u039a\u0391\u03a3\u03a3\u0395', 'utf16le'); console.log(utf16Buffer.indexOf('\u03a3', 0, 'utf16le')); // Prints: 4 console.log(utf16Buffer.indexOf('\u03a3', -4, 'utf16le')); // Prints: 6</code></pre> <p>If <code>value</code> is not a string, number, or <code>Buffer</code>, this method will throw a <code>TypeError</code>. If <code>value</code> is a number, it will be coerced to a valid byte value, an integer between 0 and 255.</p> <p>If <code>byteOffset</code> is not a number, it will be coerced to a number. If the result of coercion is <code>NaN</code> or <code>0</code>, then the entire buffer will be searched. This behavior matches <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/indexOf"><code>String#indexOf()</code></a>.</p> <pre><code class="language-js">const b = Buffer.from('abcdef'); // Passing a value that's a number, but not a valid byte // Prints: 2, equivalent to searching for 99 or 'c' console.log(b.indexOf(99.9)); console.log(b.indexOf(256 + 99)); // Passing a byteOffset that coerces to NaN or 0 // Prints: 1, searching the whole buffer console.log(b.indexOf('b', undefined)); console.log(b.indexOf('b', {})); console.log(b.indexOf('b', null)); console.log(b.indexOf('b', []));</code></pre> <p>If <code>value</code> is an empty string or empty <code>Buffer</code> and <code>byteOffset</code> is less than <code>buf.length</code>, <code>byteOffset</code> will be returned. If <code>value</code> is empty and <code>byteOffset</code> is at least <code>buf.length</code>, <code>buf.length</code> will be returned.</p> <h3>buf.keys()<span><a class="mark" href="#buffer_buf_keys" id="buffer_buf_keys">#</a></span></h3> <div class="api_metadata"> <span>Added in: v1.1.0</span> </div><ul> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#The_iterator_protocol" class="type"><Iterator></a></li> </ul> <p>Creates and returns an <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols">iterator</a> of <code>buf</code> keys (indices).</p> <pre><code class="language-js">const buf = Buffer.from('buffer'); for (const key of buf.keys()) { console.log(key); } // Prints: // 0 // 1 // 2 // 3 // 4 // 5</code></pre> <h3>buf.lastIndexOf(value[, byteOffset][, encoding])<span><a class="mark" href="#buffer_buf_lastindexof_value_byteoffset_encoding" id="buffer_buf_lastindexof_value_byteoffset_encoding">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v8.0.0</td> <td><p>The <code>value</code> can now be a <code>Uint8Array</code>.</p> </td></tr> <tr><td>v6.0.0</td> <td><p><span>Added in: v6.0.0</span></p> </td></tr> </table> </details> </div><ul> <li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> | <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array" class="type"><Uint8Array></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> What to search for.</li> <li><code>byteOffset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Where to begin searching in <code>buf</code>. <strong>Default:</strong> <a href="#buffer_buf_length"><code>buf.length</code></a><code>- 1</code>.</li> <li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> If <code>value</code> is a string, this is the encoding used to determine the binary representation of the string that will be searched for in <code>buf</code>. <strong>Default:</strong> <code>'utf8'</code>.</li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The index of the last occurrence of <code>value</code> in <code>buf</code>, or <code>-1</code> if <code>buf</code> does not contain <code>value</code>.</li> </ul> <p>Identical to <a href="#buffer_buf_indexof_value_byteoffset_encoding"><code>buf.indexOf()</code></a>, except the last occurrence of <code>value</code> is found rather than the first occurrence.</p> <pre><code class="language-js">const buf = Buffer.from('this buffer is a buffer'); console.log(buf.lastIndexOf('this')); // Prints: 0 console.log(buf.lastIndexOf('buffer')); // Prints: 17 console.log(buf.lastIndexOf(Buffer.from('buffer'))); // Prints: 17 console.log(buf.lastIndexOf(97)); // Prints: 15 (97 is the decimal ASCII value for 'a') console.log(buf.lastIndexOf(Buffer.from('yolo'))); // Prints: -1 console.log(buf.lastIndexOf('buffer', 5)); // Prints: 5 console.log(buf.lastIndexOf('buffer', 4)); // Prints: -1 const utf16Buffer = Buffer.from('\u039a\u0391\u03a3\u03a3\u0395', 'utf16le'); console.log(utf16Buffer.lastIndexOf('\u03a3', undefined, 'utf16le')); // Prints: 6 console.log(utf16Buffer.lastIndexOf('\u03a3', -5, 'utf16le')); // Prints: 4</code></pre> <p>If <code>value</code> is not a string, number, or <code>Buffer</code>, this method will throw a <code>TypeError</code>. If <code>value</code> is a number, it will be coerced to a valid byte value, an integer between 0 and 255.</p> <p>If <code>byteOffset</code> is not a number, it will be coerced to a number. Any arguments that coerce to <code>NaN</code>, like <code>{}</code> or <code>undefined</code>, will search the whole buffer. This behavior matches <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/lastIndexOf"><code>String#lastIndexOf()</code></a>.</p> <pre><code class="language-js">const b = Buffer.from('abcdef'); // Passing a value that's a number, but not a valid byte // Prints: 2, equivalent to searching for 99 or 'c' console.log(b.lastIndexOf(99.9)); console.log(b.lastIndexOf(256 + 99)); // Passing a byteOffset that coerces to NaN // Prints: 1, searching the whole buffer console.log(b.lastIndexOf('b', undefined)); console.log(b.lastIndexOf('b', {})); // Passing a byteOffset that coerces to 0 // Prints: -1, equivalent to passing 0 console.log(b.lastIndexOf('b', null)); console.log(b.lastIndexOf('b', []));</code></pre> <p>If <code>value</code> is an empty string or empty <code>Buffer</code>, <code>byteOffset</code> will be returned.</p> <h3>buf.length<span><a class="mark" href="#buffer_buf_length" id="buffer_buf_length">#</a></span></h3> <div class="api_metadata"> <span>Added in: v0.1.90</span> </div><ul> <li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> </ul> <p>Returns the amount of memory allocated for <code>buf</code> in bytes. Note that this does not necessarily reflect the amount of "usable" data within <code>buf</code>.</p> <pre><code class="language-js">// Create a `Buffer` and write a shorter ASCII string to it. const buf = Buffer.alloc(1234); console.log(buf.length); // Prints: 1234 buf.write('some string', 0, 'ascii'); console.log(buf.length); // Prints: 1234</code></pre> <p>While the <code>length</code> property is not immutable, changing the value of <code>length</code> can result in undefined and inconsistent behavior. Applications that wish to modify the length of a <code>Buffer</code> should therefore treat <code>length</code> as read-only and use <a href="#buffer_buf_slice_start_end"><code>buf.slice()</code></a> to create a new <code>Buffer</code>.</p> <pre><code class="language-js">let buf = Buffer.allocUnsafe(10); buf.write('abcdefghj', 0, 'ascii'); console.log(buf.length); // Prints: 10 buf = buf.slice(0, 5); console.log(buf.length); // Prints: 5</code></pre> <h3>buf.parent<span><a class="mark" href="#buffer_buf_parent" id="buffer_buf_parent">#</a></span></h3> <div class="api_metadata"> <span>Deprecated since: v8.0.0</span> </div><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use [`buf.buffer`] instead.</div><p>The <code>buf.parent</code> property is a deprecated alias for <code>buf.buffer</code>.</p> <h3>buf.readDoubleBE(offset)<span><a class="mark" href="#buffer_buf_readdoublebe_offset" id="buffer_buf_readdoublebe_offset">#</a></span></h3> <h3>buf.readDoubleLE(offset)<span><a class="mark" href="#buffer_buf_readdoublele_offset" id="buffer_buf_readdoublele_offset">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v10.0.0</td> <td><p>Removed <code>noAssert</code> and no implicit coercion of the offset to <code>uint32</code> anymore.</p> </td></tr> <tr><td>v0.11.15</td> <td><p><span>Added in: v0.11.15</span></p> </td></tr> </table> </details> </div><ul> <li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to read. Must satisfy <code>0 <= offset <= buf.length - 8</code>.</li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> </ul> <p>Reads a 64-bit double from <code>buf</code> at the specified <code>offset</code> with specified endian format (<code>readDoubleBE()</code> returns big endian, <code>readDoubleLE()</code> returns little endian).</p> <pre><code class="language-js">const buf = Buffer.from([1, 2, 3, 4, 5, 6, 7, 8]); console.log(buf.readDoubleBE(0)); // Prints: 8.20788039913184e-304 console.log(buf.readDoubleLE(0)); // Prints: 5.447603722011605e-270 console.log(buf.readDoubleLE(1)); // Throws ERR_OUT_OF_RANGE</code></pre> <h3>buf.readFloatBE(offset)<span><a class="mark" href="#buffer_buf_readfloatbe_offset" id="buffer_buf_readfloatbe_offset">#</a></span></h3> <h3>buf.readFloatLE(offset)<span><a class="mark" href="#buffer_buf_readfloatle_offset" id="buffer_buf_readfloatle_offset">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v10.0.0</td> <td><p>Removed <code>noAssert</code> and no implicit coercion of the offset to <code>uint32</code> anymore.</p> </td></tr> <tr><td>v0.11.15</td> <td><p><span>Added in: v0.11.15</span></p> </td></tr> </table> </details> </div><ul> <li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to read. Must satisfy <code>0 <= offset <= buf.length - 4</code>.</li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a></li> </ul> <p>Reads a 32-bit float from <code>buf</code> at the specified <code>offset</code> with specified endian format (<code>readFloatBE()</code> returns big endian, <code>readFloatLE()</code> returns little endian).</p> <pre><code class="language-js">const buf = Buffer.from([1, 2, 3, 4]); console.log(buf.readFloatBE(0)); // Prints: 2.387939260590663e-38 console.log(buf.readFloatLE(0)); // Prints: 1.539989614439558e-36 console.log(buf.readFloatLE(1)); // Throws ERR_OUT_OF_RANGE</code></pre> <h3>buf.readInt8(offset)<span><a class="mark" href="#buffer_buf_readint8_offset" id="buffer_buf_readint8_offset">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v10.0.0</td> <td><p>Removed <code>noAssert</code> and no implicit coercion of the offset to <code>uint32</code> anymore.</p> </td></tr> <tr><td>v0.5.0</td> <td><p><span>Added in: v0.5.0</span></p> </td></tr> </table> </details> </div><ul> <li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to read. Must satisfy <code>0 <= offset <= buf.length - 1</code>.</li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> </ul> <p>Reads a signed 8-bit integer from <code>buf</code> at the specified <code>offset</code>.</p> <p>Integers read from a <code>Buffer</code> are interpreted as two's complement signed values.</p> <pre><code class="language-js">const buf = Buffer.from([-1, 5]); console.log(buf.readInt8(0)); // Prints: -1 console.log(buf.readInt8(1)); // Prints: 5 console.log(buf.readInt8(2)); // Throws ERR_OUT_OF_RANGE</code></pre> <h3>buf.readInt16BE(offset)<span><a class="mark" href="#buffer_buf_readint16be_offset" id="buffer_buf_readint16be_offset">#</a></span></h3> <h3>buf.readInt16LE(offset)<span><a class="mark" href="#buffer_buf_readint16le_offset" id="buffer_buf_readint16le_offset">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v10.0.0</td> <td><p>Removed <code>noAssert</code> and no implicit coercion of the offset to <code>uint32</code> anymore.</p> </td></tr> <tr><td>v0.5.5</td> <td><p><span>Added in: v0.5.5</span></p> </td></tr> </table> </details> </div><ul> <li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to read. Must satisfy <code>0 <= offset <= buf.length - 2</code>.</li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> </ul> <p>Reads a signed 16-bit integer from <code>buf</code> at the specified <code>offset</code> with the specified endian format (<code>readInt16BE()</code> returns big endian, <code>readInt16LE()</code> returns little endian).</p> <p>Integers read from a <code>Buffer</code> are interpreted as two's complement signed values.</p> <pre><code class="language-js">const buf = Buffer.from([0, 5]); console.log(buf.readInt16BE(0)); // Prints: 5 console.log(buf.readInt16LE(0)); // Prints: 1280 console.log(buf.readInt16LE(1)); // Throws ERR_OUT_OF_RANGE</code></pre> <h3>buf.readInt32BE(offset)<span><a class="mark" href="#buffer_buf_readint32be_offset" id="buffer_buf_readint32be_offset">#</a></span></h3> <h3>buf.readInt32LE(offset)<span><a class="mark" href="#buffer_buf_readint32le_offset" id="buffer_buf_readint32le_offset">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v10.0.0</td> <td><p>Removed <code>noAssert</code> and no implicit coercion of the offset to <code>uint32</code> anymore.</p> </td></tr> <tr><td>v0.5.5</td> <td><p><span>Added in: v0.5.5</span></p> </td></tr> </table> </details> </div><ul> <li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to read. Must satisfy <code>0 <= offset <= buf.length - 4</code>.</li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> </ul> <p>Reads a signed 32-bit integer from <code>buf</code> at the specified <code>offset</code> with the specified endian format (<code>readInt32BE()</code> returns big endian, <code>readInt32LE()</code> returns little endian).</p> <p>Integers read from a <code>Buffer</code> are interpreted as two's complement signed values.</p> <pre><code class="language-js">const buf = Buffer.from([0, 0, 0, 5]); console.log(buf.readInt32BE(0)); // Prints: 5 console.log(buf.readInt32LE(0)); // Prints: 83886080 console.log(buf.readInt32LE(1)); // Throws ERR_OUT_OF_RANGE</code></pre> <h3>buf.readIntBE(offset, byteLength)<span><a class="mark" href="#buffer_buf_readintbe_offset_bytelength" id="buffer_buf_readintbe_offset_bytelength">#</a></span></h3> <h3>buf.readIntLE(offset, byteLength)<span><a class="mark" href="#buffer_buf_readintle_offset_bytelength" id="buffer_buf_readintle_offset_bytelength">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v10.0.0</td> <td><p>Removed <code>noAssert</code> and no implicit coercion of the offset and <code>byteLength</code> to <code>uint32</code> anymore.</p> </td></tr> <tr><td>v0.11.15</td> <td><p><span>Added in: v0.11.15</span></p> </td></tr> </table> </details> </div><ul> <li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to read. Must satisfy <code>0 <= offset <= buf.length - byteLength</code>.</li> <li><code>byteLength</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to read. Must satisfy <code>0 < byteLength <= 6</code>.</li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> </ul> <p>Reads <code>byteLength</code> number of bytes from <code>buf</code> at the specified <code>offset</code> and interprets the result as a two's complement signed value. Supports up to 48 bits of accuracy.</p> <pre><code class="language-js">const buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]); console.log(buf.readIntLE(0, 6).toString(16)); // Prints: -546f87a9cbee console.log(buf.readIntBE(0, 6).toString(16)); // Prints: 1234567890ab console.log(buf.readIntBE(1, 6).toString(16)); // Throws ERR_INDEX_OUT_OF_RANGE console.log(buf.readIntBE(1, 0).toString(16)); // Throws ERR_OUT_OF_RANGE</code></pre> <h3>buf.readUInt8(offset)<span><a class="mark" href="#buffer_buf_readuint8_offset" id="buffer_buf_readuint8_offset">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v10.0.0</td> <td><p>Removed <code>noAssert</code> and no implicit coercion of the offset to <code>uint32</code> anymore.</p> </td></tr> <tr><td>v0.5.0</td> <td><p><span>Added in: v0.5.0</span></p> </td></tr> </table> </details> </div><ul> <li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to read. Must satisfy <code>0 <= offset <= buf.length - 1</code>.</li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> </ul> <p>Reads an unsigned 8-bit integer from <code>buf</code> at the specified <code>offset</code>.</p> <pre><code class="language-js">const buf = Buffer.from([1, -2]); console.log(buf.readUInt8(0)); // Prints: 1 console.log(buf.readUInt8(1)); // Prints: 254 console.log(buf.readUInt8(2)); // Throws ERR_OUT_OF_RANGE</code></pre> <h3>buf.readUInt16BE(offset)<span><a class="mark" href="#buffer_buf_readuint16be_offset" id="buffer_buf_readuint16be_offset">#</a></span></h3> <h3>buf.readUInt16LE(offset)<span><a class="mark" href="#buffer_buf_readuint16le_offset" id="buffer_buf_readuint16le_offset">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v10.0.0</td> <td><p>Removed <code>noAssert</code> and no implicit coercion of the offset to <code>uint32</code> anymore.</p> </td></tr> <tr><td>v0.5.5</td> <td><p><span>Added in: v0.5.5</span></p> </td></tr> </table> </details> </div><ul> <li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to read. Must satisfy <code>0 <= offset <= buf.length - 2</code>.</li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> </ul> <p>Reads an unsigned 16-bit integer from <code>buf</code> at the specified <code>offset</code> with specified endian format (<code>readUInt16BE()</code> returns big endian, <code>readUInt16LE()</code> returns little endian).</p> <pre><code class="language-js">const buf = Buffer.from([0x12, 0x34, 0x56]); console.log(buf.readUInt16BE(0).toString(16)); // Prints: 1234 console.log(buf.readUInt16LE(0).toString(16)); // Prints: 3412 console.log(buf.readUInt16BE(1).toString(16)); // Prints: 3456 console.log(buf.readUInt16LE(1).toString(16)); // Prints: 5634 console.log(buf.readUInt16LE(2).toString(16)); // Throws ERR_OUT_OF_RANGE</code></pre> <h3>buf.readUInt32BE(offset)<span><a class="mark" href="#buffer_buf_readuint32be_offset" id="buffer_buf_readuint32be_offset">#</a></span></h3> <h3>buf.readUInt32LE(offset)<span><a class="mark" href="#buffer_buf_readuint32le_offset" id="buffer_buf_readuint32le_offset">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v10.0.0</td> <td><p>Removed <code>noAssert</code> and no implicit coercion of the offset to <code>uint32</code> anymore.</p> </td></tr> <tr><td>v0.5.5</td> <td><p><span>Added in: v0.5.5</span></p> </td></tr> </table> </details> </div><ul> <li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to read. Must satisfy <code>0 <= offset <= buf.length - 4</code>.</li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> </ul> <p>Reads an unsigned 32-bit integer from <code>buf</code> at the specified <code>offset</code> with specified endian format (<code>readUInt32BE()</code> returns big endian, <code>readUInt32LE()</code> returns little endian).</p> <pre><code class="language-js">const buf = Buffer.from([0x12, 0x34, 0x56, 0x78]); console.log(buf.readUInt32BE(0).toString(16)); // Prints: 12345678 console.log(buf.readUInt32LE(0).toString(16)); // Prints: 78563412 console.log(buf.readUInt32LE(1).toString(16)); // Throws ERR_OUT_OF_RANGE</code></pre> <h3>buf.readUIntBE(offset, byteLength)<span><a class="mark" href="#buffer_buf_readuintbe_offset_bytelength" id="buffer_buf_readuintbe_offset_bytelength">#</a></span></h3> <h3>buf.readUIntLE(offset, byteLength)<span><a class="mark" href="#buffer_buf_readuintle_offset_bytelength" id="buffer_buf_readuintle_offset_bytelength">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v10.0.0</td> <td><p>Removed <code>noAssert</code> and no implicit coercion of the offset and <code>byteLength</code> to <code>uint32</code> anymore.</p> </td></tr> <tr><td>v0.11.15</td> <td><p><span>Added in: v0.11.15</span></p> </td></tr> </table> </details> </div><ul> <li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to read. Must satisfy <code>0 <= offset <= buf.length - byteLength</code>.</li> <li><code>byteLength</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to read. Must satisfy <code>0 < byteLength <= 6</code>.</li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a></li> </ul> <p>Reads <code>byteLength</code> number of bytes from <code>buf</code> at the specified <code>offset</code> and interprets the result as an unsigned integer. Supports up to 48 bits of accuracy.</p> <pre><code class="language-js">const buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]); console.log(buf.readUIntBE(0, 6).toString(16)); // Prints: 1234567890ab console.log(buf.readUIntLE(0, 6).toString(16)); // Prints: ab9078563412 console.log(buf.readUIntBE(1, 6).toString(16)); // Throws ERR_OUT_OF_RANGE</code></pre> <h3>buf.slice([start[, end]])<span><a class="mark" href="#buffer_buf_slice_start_end" id="buffer_buf_slice_start_end">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v7.1.0, v6.9.2</td> <td><p>Coercing the offsets to integers now handles values outside the 32-bit integer range properly.</p> </td></tr> <tr><td>v7.0.0</td> <td><p>All offsets are now coerced to integers before doing any calculations with them.</p> </td></tr> <tr><td>v0.3.0</td> <td><p><span>Added in: v0.3.0</span></p> </td></tr> </table> </details> </div><ul> <li><code>start</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Where the new <code>Buffer</code> will start. <strong>Default:</strong> <code>0</code>.</li> <li><code>end</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Where the new <code>Buffer</code> will end (not inclusive). <strong>Default:</strong> <a href="#buffer_buf_length"><code>buf.length</code></a>.</li> <li>Returns: <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a></li> </ul> <p>Returns a new <code>Buffer</code> that references the same memory as the original, but offset and cropped by the <code>start</code> and <code>end</code> indices.</p> <p>Specifying <code>end</code> greater than <a href="#buffer_buf_length"><code>buf.length</code></a> will return the same result as that of <code>end</code> equal to <a href="#buffer_buf_length"><code>buf.length</code></a>.</p> <p>Modifying the new <code>Buffer</code> slice will modify the memory in the original <code>Buffer</code> because the allocated memory of the two objects overlap.</p> <pre><code class="language-js">// Create a `Buffer` with the ASCII alphabet, take a slice, and modify one byte // from the original `Buffer`. const buf1 = Buffer.allocUnsafe(26); for (let i = 0; i < 26; i++) { // 97 is the decimal ASCII value for 'a' buf1[i] = i + 97; } const buf2 = buf1.slice(0, 3); console.log(buf2.toString('ascii', 0, buf2.length)); // Prints: abc buf1[0] = 33; console.log(buf2.toString('ascii', 0, buf2.length)); // Prints: !bc</code></pre> <p>Specifying negative indexes causes the slice to be generated relative to the end of <code>buf</code> rather than the beginning.</p> <pre><code class="language-js">const buf = Buffer.from('buffer'); console.log(buf.slice(-6, -1).toString()); // Prints: buffe // (Equivalent to buf.slice(0, 5)) console.log(buf.slice(-6, -2).toString()); // Prints: buff // (Equivalent to buf.slice(0, 4)) console.log(buf.slice(-5, -2).toString()); // Prints: uff // (Equivalent to buf.slice(1, 4))</code></pre> <h3>buf.swap16()<span><a class="mark" href="#buffer_buf_swap16" id="buffer_buf_swap16">#</a></span></h3> <div class="api_metadata"> <span>Added in: v5.10.0</span> </div><ul> <li>Returns: <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> A reference to <code>buf</code>.</li> </ul> <p>Interprets <code>buf</code> as an array of unsigned 16-bit integers and swaps the byte order <em>in-place</em>. Throws <a href="errors.html#ERR_INVALID_BUFFER_SIZE"><code>ERR_INVALID_BUFFER_SIZE</code></a> if <a href="#buffer_buf_length"><code>buf.length</code></a> is not a multiple of 2.</p> <pre><code class="language-js">const buf1 = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]); console.log(buf1); // Prints: <Buffer 01 02 03 04 05 06 07 08> buf1.swap16(); console.log(buf1); // Prints: <Buffer 02 01 04 03 06 05 08 07> const buf2 = Buffer.from([0x1, 0x2, 0x3]); buf2.swap16(); // Throws ERR_INVALID_BUFFER_SIZE</code></pre> <p>One convenient use of <code>buf.swap16()</code> is to perform a fast in-place conversion between UTF-16 little-endian and UTF-16 big-endian:</p> <pre><code class="language-js">const buf = Buffer.from('This is little-endian UTF-16', 'utf16le'); buf.swap16(); // Convert to big-endian UTF-16 text.</code></pre> <h3>buf.swap32()<span><a class="mark" href="#buffer_buf_swap32" id="buffer_buf_swap32">#</a></span></h3> <div class="api_metadata"> <span>Added in: v5.10.0</span> </div><ul> <li>Returns: <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> A reference to <code>buf</code>.</li> </ul> <p>Interprets <code>buf</code> as an array of unsigned 32-bit integers and swaps the byte order <em>in-place</em>. Throws <a href="errors.html#ERR_INVALID_BUFFER_SIZE"><code>ERR_INVALID_BUFFER_SIZE</code></a> if <a href="#buffer_buf_length"><code>buf.length</code></a> is not a multiple of 4.</p> <pre><code class="language-js">const buf1 = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]); console.log(buf1); // Prints: <Buffer 01 02 03 04 05 06 07 08> buf1.swap32(); console.log(buf1); // Prints: <Buffer 04 03 02 01 08 07 06 05> const buf2 = Buffer.from([0x1, 0x2, 0x3]); buf2.swap32(); // Throws ERR_INVALID_BUFFER_SIZE</code></pre> <h3>buf.swap64()<span><a class="mark" href="#buffer_buf_swap64" id="buffer_buf_swap64">#</a></span></h3> <div class="api_metadata"> <span>Added in: v6.3.0</span> </div><ul> <li>Returns: <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> A reference to <code>buf</code>.</li> </ul> <p>Interprets <code>buf</code> as an array of 64-bit numbers and swaps byte order <em>in-place</em>. Throws <a href="errors.html#ERR_INVALID_BUFFER_SIZE"><code>ERR_INVALID_BUFFER_SIZE</code></a> if <a href="#buffer_buf_length"><code>buf.length</code></a> is not a multiple of 8.</p> <pre><code class="language-js">const buf1 = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]); console.log(buf1); // Prints: <Buffer 01 02 03 04 05 06 07 08> buf1.swap64(); console.log(buf1); // Prints: <Buffer 08 07 06 05 04 03 02 01> const buf2 = Buffer.from([0x1, 0x2, 0x3]); buf2.swap64(); // Throws ERR_INVALID_BUFFER_SIZE</code></pre> <p>Note that JavaScript cannot encode 64-bit integers. This method is intended for working with 64-bit floats.</p> <h3>buf.toJSON()<span><a class="mark" href="#buffer_buf_tojson" id="buffer_buf_tojson">#</a></span></h3> <div class="api_metadata"> <span>Added in: v0.9.2</span> </div><ul> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a></li> </ul> <p>Returns a JSON representation of <code>buf</code>. <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify"><code>JSON.stringify()</code></a> implicitly calls this function when stringifying a <code>Buffer</code> instance.</p> <pre><code class="language-js">const buf = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5]); const json = JSON.stringify(buf); console.log(json); // Prints: {"type":"Buffer","data":[1,2,3,4,5]} const copy = JSON.parse(json, (key, value) => { return value && value.type === 'Buffer' ? Buffer.from(value.data) : value; }); console.log(copy); // Prints: <Buffer 01 02 03 04 05></code></pre> <h3>buf.toString([encoding[, start[, end]]])<span><a class="mark" href="#buffer_buf_tostring_encoding_start_end" id="buffer_buf_tostring_encoding_start_end">#</a></span></h3> <div class="api_metadata"> <span>Added in: v0.1.90</span> </div><ul> <li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The character encoding to use. <strong>Default:</strong> <code>'utf8'</code>.</li> <li><code>start</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The byte offset to start decoding at. <strong>Default:</strong> <code>0</code>.</li> <li><code>end</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The byte offset to stop decoding at (not inclusive). <strong>Default:</strong> <a href="#buffer_buf_length"><code>buf.length</code></a>.</li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a></li> </ul> <p>Decodes <code>buf</code> to a string according to the specified character encoding in <code>encoding</code>. <code>start</code> and <code>end</code> may be passed to decode only a subset of <code>buf</code>.</p> <p>The maximum length of a string instance (in UTF-16 code units) is available as <a href="#buffer_buffer_constants_max_string_length"><code>buffer.constants.MAX_STRING_LENGTH</code></a>.</p> <pre><code class="language-js">const buf1 = Buffer.allocUnsafe(26); for (let i = 0; i < 26; i++) { // 97 is the decimal ASCII value for 'a' buf1[i] = i + 97; } console.log(buf1.toString('ascii')); // Prints: abcdefghijklmnopqrstuvwxyz console.log(buf1.toString('ascii', 0, 5)); // Prints: abcde const buf2 = Buffer.from('tést'); console.log(buf2.toString('hex')); // Prints: 74c3a97374 console.log(buf2.toString('utf8', 0, 3)); // Prints: té console.log(buf2.toString(undefined, 0, 3)); // Prints: té</code></pre> <h3>buf.values()<span><a class="mark" href="#buffer_buf_values" id="buffer_buf_values">#</a></span></h3> <div class="api_metadata"> <span>Added in: v1.1.0</span> </div><ul> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#The_iterator_protocol" class="type"><Iterator></a></li> </ul> <p>Creates and returns an <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols">iterator</a> for <code>buf</code> values (bytes). This function is called automatically when a <code>Buffer</code> is used in a <code>for..of</code> statement.</p> <pre><code class="language-js">const buf = Buffer.from('buffer'); for (const value of buf.values()) { console.log(value); } // Prints: // 98 // 117 // 102 // 102 // 101 // 114 for (const value of buf) { console.log(value); } // Prints: // 98 // 117 // 102 // 102 // 101 // 114</code></pre> <h3>buf.write(string[, offset[, length]][, encoding])<span><a class="mark" href="#buffer_buf_write_string_offset_length_encoding" id="buffer_buf_write_string_offset_length_encoding">#</a></span></h3> <div class="api_metadata"> <span>Added in: v0.1.90</span> </div><ul> <li><code>string</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> String to write to <code>buf</code>.</li> <li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to write <code>string</code>. <strong>Default:</strong> <code>0</code>.</li> <li><code>length</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to write. <strong>Default:</strong> <code>buf.length - offset</code>.</li> <li><code>encoding</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The character encoding of <code>string</code>. <strong>Default:</strong> <code>'utf8'</code>.</li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes written.</li> </ul> <p>Writes <code>string</code> to <code>buf</code> at <code>offset</code> according to the character encoding in <code>encoding</code>. The <code>length</code> parameter is the number of bytes to write. If <code>buf</code> did not contain enough space to fit the entire string, only part of <code>string</code> will be written. However, partially encoded characters will not be written.</p> <pre><code class="language-js">const buf = Buffer.alloc(256); const len = buf.write('\u00bd + \u00bc = \u00be', 0); console.log(`${len} bytes: ${buf.toString('utf8', 0, len)}`); // Prints: 12 bytes: ½ + ¼ = ¾</code></pre> <h3>buf.writeDoubleBE(value, offset)<span><a class="mark" href="#buffer_buf_writedoublebe_value_offset" id="buffer_buf_writedoublebe_value_offset">#</a></span></h3> <h3>buf.writeDoubleLE(value, offset)<span><a class="mark" href="#buffer_buf_writedoublele_value_offset" id="buffer_buf_writedoublele_value_offset">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v10.0.0</td> <td><p>Removed <code>noAssert</code> and no implicit coercion of the offset to <code>uint32</code> anymore.</p> </td></tr> <tr><td>v0.11.15</td> <td><p><span>Added in: v0.11.15</span></p> </td></tr> </table> </details> </div><ul> <li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Number to be written to <code>buf</code>.</li> <li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to write. Must satisfy <code>0 <= offset <= buf.length - 8</code>.</li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> <code>offset</code> plus the number of bytes written.</li> </ul> <p>Writes <code>value</code> to <code>buf</code> at the specified <code>offset</code> with specified endian format (<code>writeDoubleBE()</code> writes big endian, <code>writeDoubleLE()</code> writes little endian). <code>value</code> <em>should</em> be a valid 64-bit double. Behavior is undefined when <code>value</code> is anything other than a 64-bit double.</p> <pre><code class="language-js">const buf = Buffer.allocUnsafe(8); buf.writeDoubleBE(123.456, 0); console.log(buf); // Prints: <Buffer 40 5e dd 2f 1a 9f be 77> buf.writeDoubleLE(123.456, 0); console.log(buf); // Prints: <Buffer 77 be 9f 1a 2f dd 5e 40></code></pre> <h3>buf.writeFloatBE(value, offset)<span><a class="mark" href="#buffer_buf_writefloatbe_value_offset" id="buffer_buf_writefloatbe_value_offset">#</a></span></h3> <h3>buf.writeFloatLE(value, offset)<span><a class="mark" href="#buffer_buf_writefloatle_value_offset" id="buffer_buf_writefloatle_value_offset">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v10.0.0</td> <td><p>Removed <code>noAssert</code> and no implicit coercion of the offset to <code>uint32</code> anymore.</p> </td></tr> <tr><td>v0.11.15</td> <td><p><span>Added in: v0.11.15</span></p> </td></tr> </table> </details> </div><ul> <li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><number></a> Number to be written to <code>buf</code>.</li> <li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to write. Must satisfy <code>0 <= offset <= buf.length - 4</code>.</li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> <code>offset</code> plus the number of bytes written.</li> </ul> <p>Writes <code>value</code> to <code>buf</code> at the specified <code>offset</code> with specified endian format (<code>writeFloatBE()</code> writes big endian, <code>writeFloatLE()</code> writes little endian). <code>value</code> <em>should</em> be a valid 32-bit float. Behavior is undefined when <code>value</code> is anything other than a 32-bit float.</p> <pre><code class="language-js">const buf = Buffer.allocUnsafe(4); buf.writeFloatBE(0xcafebabe, 0); console.log(buf); // Prints: <Buffer 4f 4a fe bb> buf.writeFloatLE(0xcafebabe, 0); console.log(buf); // Prints: <Buffer bb fe 4a 4f></code></pre> <h3>buf.writeInt8(value, offset)<span><a class="mark" href="#buffer_buf_writeint8_value_offset" id="buffer_buf_writeint8_value_offset">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v10.0.0</td> <td><p>Removed <code>noAssert</code> and no implicit coercion of the offset to <code>uint32</code> anymore.</p> </td></tr> <tr><td>v0.5.0</td> <td><p><span>Added in: v0.5.0</span></p> </td></tr> </table> </details> </div><ul> <li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number to be written to <code>buf</code>.</li> <li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to write. Must satisfy <code>0 <= offset <= buf.length - 1</code>.</li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> <code>offset</code> plus the number of bytes written.</li> </ul> <p>Writes <code>value</code> to <code>buf</code> at the specified <code>offset</code>. <code>value</code> <em>should</em> be a valid signed 8-bit integer. Behavior is undefined when <code>value</code> is anything other than a signed 8-bit integer.</p> <p><code>value</code> is interpreted and written as a two's complement signed integer.</p> <pre><code class="language-js">const buf = Buffer.allocUnsafe(2); buf.writeInt8(2, 0); buf.writeInt8(-2, 1); console.log(buf); // Prints: <Buffer 02 fe></code></pre> <h3>buf.writeInt16BE(value, offset)<span><a class="mark" href="#buffer_buf_writeint16be_value_offset" id="buffer_buf_writeint16be_value_offset">#</a></span></h3> <h3>buf.writeInt16LE(value, offset)<span><a class="mark" href="#buffer_buf_writeint16le_value_offset" id="buffer_buf_writeint16le_value_offset">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v10.0.0</td> <td><p>Removed <code>noAssert</code> and no implicit coercion of the offset to <code>uint32</code> anymore.</p> </td></tr> <tr><td>v0.5.5</td> <td><p><span>Added in: v0.5.5</span></p> </td></tr> </table> </details> </div><ul> <li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number to be written to <code>buf</code>.</li> <li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to write. Must satisfy <code>0 <= offset <= buf.length - 2</code>.</li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> <code>offset</code> plus the number of bytes written.</li> </ul> <p>Writes <code>value</code> to <code>buf</code> at the specified <code>offset</code> with specified endian format (<code>writeInt16BE()</code> writes big endian, <code>writeInt16LE()</code> writes little endian). <code>value</code> <em>should</em> be a valid signed 16-bit integer. Behavior is undefined when <code>value</code> is anything other than a signed 16-bit integer.</p> <p><code>value</code> is interpreted and written as a two's complement signed integer.</p> <pre><code class="language-js">const buf = Buffer.allocUnsafe(4); buf.writeInt16BE(0x0102, 0); buf.writeInt16LE(0x0304, 2); console.log(buf); // Prints: <Buffer 01 02 04 03></code></pre> <h3>buf.writeInt32BE(value, offset)<span><a class="mark" href="#buffer_buf_writeint32be_value_offset" id="buffer_buf_writeint32be_value_offset">#</a></span></h3> <h3>buf.writeInt32LE(value, offset)<span><a class="mark" href="#buffer_buf_writeint32le_value_offset" id="buffer_buf_writeint32le_value_offset">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v10.0.0</td> <td><p>Removed <code>noAssert</code> and no implicit coercion of the offset to <code>uint32</code> anymore.</p> </td></tr> <tr><td>v0.5.5</td> <td><p><span>Added in: v0.5.5</span></p> </td></tr> </table> </details> </div><ul> <li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number to be written to <code>buf</code>.</li> <li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to write. Must satisfy <code>0 <= offset <= buf.length - 4</code>.</li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> <code>offset</code> plus the number of bytes written.</li> </ul> <p>Writes <code>value</code> to <code>buf</code> at the specified <code>offset</code> with specified endian format (<code>writeInt32BE()</code> writes big endian, <code>writeInt32LE()</code> writes little endian). <code>value</code> <em>should</em> be a valid signed 32-bit integer. Behavior is undefined when <code>value</code> is anything other than a signed 32-bit integer.</p> <p><code>value</code> is interpreted and written as a two's complement signed integer.</p> <pre><code class="language-js">const buf = Buffer.allocUnsafe(8); buf.writeInt32BE(0x01020304, 0); buf.writeInt32LE(0x05060708, 4); console.log(buf); // Prints: <Buffer 01 02 03 04 08 07 06 05></code></pre> <h3>buf.writeIntBE(value, offset, byteLength)<span><a class="mark" href="#buffer_buf_writeintbe_value_offset_bytelength" id="buffer_buf_writeintbe_value_offset_bytelength">#</a></span></h3> <h3>buf.writeIntLE(value, offset, byteLength)<span><a class="mark" href="#buffer_buf_writeintle_value_offset_bytelength" id="buffer_buf_writeintle_value_offset_bytelength">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v10.0.0</td> <td><p>Removed <code>noAssert</code> and no implicit coercion of the offset and <code>byteLength</code> to <code>uint32</code> anymore.</p> </td></tr> <tr><td>v0.11.15</td> <td><p><span>Added in: v0.11.15</span></p> </td></tr> </table> </details> </div><ul> <li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number to be written to <code>buf</code>.</li> <li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to write. Must satisfy <code>0 <= offset <= buf.length - byteLength</code>.</li> <li><code>byteLength</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to write. Must satisfy <code>0 < byteLength <= 6</code>.</li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> <code>offset</code> plus the number of bytes written.</li> </ul> <p>Writes <code>byteLength</code> bytes of <code>value</code> to <code>buf</code> at the specified <code>offset</code>. Supports up to 48 bits of accuracy. Behavior is undefined when <code>value</code> is anything other than a signed integer.</p> <pre><code class="language-js">const buf = Buffer.allocUnsafe(6); buf.writeIntBE(0x1234567890ab, 0, 6); console.log(buf); // Prints: <Buffer 12 34 56 78 90 ab> buf.writeIntLE(0x1234567890ab, 0, 6); console.log(buf); // Prints: <Buffer ab 90 78 56 34 12></code></pre> <h3>buf.writeUInt8(value, offset)<span><a class="mark" href="#buffer_buf_writeuint8_value_offset" id="buffer_buf_writeuint8_value_offset">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v10.0.0</td> <td><p>Removed <code>noAssert</code> and no implicit coercion of the offset to <code>uint32</code> anymore.</p> </td></tr> <tr><td>v0.5.0</td> <td><p><span>Added in: v0.5.0</span></p> </td></tr> </table> </details> </div><ul> <li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number to be written to <code>buf</code>.</li> <li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to write. Must satisfy <code>0 <= offset <= buf.length - 1</code>.</li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> <code>offset</code> plus the number of bytes written.</li> </ul> <p>Writes <code>value</code> to <code>buf</code> at the specified <code>offset</code>. <code>value</code> <em>should</em> be a valid unsigned 8-bit integer. Behavior is undefined when <code>value</code> is anything other than an unsigned 8-bit integer.</p> <pre><code class="language-js">const buf = Buffer.allocUnsafe(4); buf.writeUInt8(0x3, 0); buf.writeUInt8(0x4, 1); buf.writeUInt8(0x23, 2); buf.writeUInt8(0x42, 3); console.log(buf); // Prints: <Buffer 03 04 23 42></code></pre> <h3>buf.writeUInt16BE(value, offset)<span><a class="mark" href="#buffer_buf_writeuint16be_value_offset" id="buffer_buf_writeuint16be_value_offset">#</a></span></h3> <h3>buf.writeUInt16LE(value, offset)<span><a class="mark" href="#buffer_buf_writeuint16le_value_offset" id="buffer_buf_writeuint16le_value_offset">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v10.0.0</td> <td><p>Removed <code>noAssert</code> and no implicit coercion of the offset to <code>uint32</code> anymore.</p> </td></tr> <tr><td>v0.5.5</td> <td><p><span>Added in: v0.5.5</span></p> </td></tr> </table> </details> </div><ul> <li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number to be written to <code>buf</code>.</li> <li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to write. Must satisfy <code>0 <= offset <= buf.length - 2</code>.</li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> <code>offset</code> plus the number of bytes written.</li> </ul> <p>Writes <code>value</code> to <code>buf</code> at the specified <code>offset</code> with specified endian format (<code>writeUInt16BE()</code> writes big endian, <code>writeUInt16LE()</code> writes little endian). <code>value</code> should be a valid unsigned 16-bit integer. Behavior is undefined when <code>value</code> is anything other than an unsigned 16-bit integer.</p> <pre><code class="language-js">const buf = Buffer.allocUnsafe(4); buf.writeUInt16BE(0xdead, 0); buf.writeUInt16BE(0xbeef, 2); console.log(buf); // Prints: <Buffer de ad be ef> buf.writeUInt16LE(0xdead, 0); buf.writeUInt16LE(0xbeef, 2); console.log(buf); // Prints: <Buffer ad de ef be></code></pre> <h3>buf.writeUInt32BE(value, offset)<span><a class="mark" href="#buffer_buf_writeuint32be_value_offset" id="buffer_buf_writeuint32be_value_offset">#</a></span></h3> <h3>buf.writeUInt32LE(value, offset)<span><a class="mark" href="#buffer_buf_writeuint32le_value_offset" id="buffer_buf_writeuint32le_value_offset">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v10.0.0</td> <td><p>Removed <code>noAssert</code> and no implicit coercion of the offset to <code>uint32</code> anymore.</p> </td></tr> <tr><td>v0.5.5</td> <td><p><span>Added in: v0.5.5</span></p> </td></tr> </table> </details> </div><ul> <li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number to be written to <code>buf</code>.</li> <li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to write. Must satisfy <code>0 <= offset <= buf.length - 4</code>.</li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> <code>offset</code> plus the number of bytes written.</li> </ul> <p>Writes <code>value</code> to <code>buf</code> at the specified <code>offset</code> with specified endian format (<code>writeUInt32BE()</code> writes big endian, <code>writeUInt32LE()</code> writes little endian). <code>value</code> should be a valid unsigned 32-bit integer. Behavior is undefined when <code>value</code> is anything other than an unsigned 32-bit integer.</p> <pre><code class="language-js">const buf = Buffer.allocUnsafe(4); buf.writeUInt32BE(0xfeedface, 0); console.log(buf); // Prints: <Buffer fe ed fa ce> buf.writeUInt32LE(0xfeedface, 0); console.log(buf); // Prints: <Buffer ce fa ed fe></code></pre> <h3>buf.writeUIntBE(value, offset, byteLength)<span><a class="mark" href="#buffer_buf_writeuintbe_value_offset_bytelength" id="buffer_buf_writeuintbe_value_offset_bytelength">#</a></span></h3> <h3>buf.writeUIntLE(value, offset, byteLength)<span><a class="mark" href="#buffer_buf_writeuintle_value_offset_bytelength" id="buffer_buf_writeuintle_value_offset_bytelength">#</a></span></h3> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v10.0.0</td> <td><p>Removed <code>noAssert</code> and no implicit coercion of the offset and <code>byteLength</code> to <code>uint32</code> anymore.</p> </td></tr> <tr><td>v0.5.5</td> <td><p><span>Added in: v0.5.5</span></p> </td></tr> </table> </details> </div><ul> <li><code>value</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number to be written to <code>buf</code>.</li> <li><code>offset</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to skip before starting to write. Must satisfy <code>0 <= offset <= buf.length - byteLength</code>.</li> <li><code>byteLength</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> Number of bytes to write. Must satisfy <code>0 < byteLength <= 6</code>.</li> <li>Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> <code>offset</code> plus the number of bytes written.</li> </ul> <p>Writes <code>byteLength</code> bytes of <code>value</code> to <code>buf</code> at the specified <code>offset</code>. Supports up to 48 bits of accuracy. Behavior is undefined when <code>value</code> is anything other than an unsigned integer.</p> <pre><code class="language-js">const buf = Buffer.allocUnsafe(6); buf.writeUIntBE(0x1234567890ab, 0, 6); console.log(buf); // Prints: <Buffer 12 34 56 78 90 ab> buf.writeUIntLE(0x1234567890ab, 0, 6); console.log(buf); // Prints: <Buffer ab 90 78 56 34 12></code></pre> <h2>buffer.INSPECT_MAX_BYTES<span><a class="mark" href="#buffer_buffer_inspect_max_bytes" id="buffer_buffer_inspect_max_bytes">#</a></span></h2> <div class="api_metadata"> <span>Added in: v0.5.4</span> </div><ul> <li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> <strong>Default:</strong> <code>50</code></li> </ul> <p>Returns the maximum number of bytes that will be returned when <code>buf.inspect()</code> is called. This can be overridden by user modules. See <a href="util.html#util_util_inspect_object_options"><code>util.inspect()</code></a> for more details on <code>buf.inspect()</code> behavior.</p> <p>Note that this is a property on the <code>buffer</code> module returned by <code>require('buffer')</code>, not on the <code>Buffer</code> global or a <code>Buffer</code> instance.</p> <h2>buffer.kMaxLength<span><a class="mark" href="#buffer_buffer_kmaxlength" id="buffer_buffer_kmaxlength">#</a></span></h2> <div class="api_metadata"> <span>Added in: v3.0.0</span> </div><ul> <li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The largest size allowed for a single <code>Buffer</code> instance.</li> </ul> <p>An alias for <a href="#buffer_buffer_constants_max_length"><code>buffer.constants.MAX_LENGTH</code></a>.</p> <p>Note that this is a property on the <code>buffer</code> module returned by <code>require('buffer')</code>, not on the <code>Buffer</code> global or a <code>Buffer</code> instance.</p> <h2>buffer.transcode(source, fromEnc, toEnc)<span><a class="mark" href="#buffer_buffer_transcode_source_fromenc_toenc" id="buffer_buffer_transcode_source_fromenc_toenc">#</a></span></h2> <div class="api_metadata"> <details class="changelog"><summary>History</summary> <table> <tr><th>Version</th><th>Changes</th></tr> <tr><td>v8.0.0</td> <td><p>The <code>source</code> parameter can now be a <code>Uint8Array</code>.</p> </td></tr> <tr><td>v7.1.0</td> <td><p><span>Added in: v7.1.0</span></p> </td></tr> </table> </details> </div><ul> <li><code>source</code> <a href="buffer.html#buffer_class_buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array" class="type"><Uint8Array></a> A <code>Buffer</code> or <code>Uint8Array</code> instance.</li> <li><code>fromEnc</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> The current encoding.</li> <li><code>toEnc</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type" class="type"><string></a> To target encoding.</li> </ul> <p>Re-encodes the given <code>Buffer</code> or <code>Uint8Array</code> instance from one character encoding to another. Returns a new <code>Buffer</code> instance.</p> <p>Throws if the <code>fromEnc</code> or <code>toEnc</code> specify invalid character encodings or if conversion from <code>fromEnc</code> to <code>toEnc</code> is not permitted.</p> <p>Encodings supported by <code>buffer.transcode()</code> are: <code>'ascii'</code>, <code>'utf8'</code>, <code>'utf16le'</code>, <code>'ucs2'</code>, <code>'latin1'</code>, and <code>'binary'</code>.</p> <p>The transcoding process will use substitution characters if a given byte sequence cannot be adequately represented in the target encoding. For instance:</p> <pre><code class="language-js">const buffer = require('buffer'); const newBuf = buffer.transcode(Buffer.from('€'), 'utf8', 'ascii'); console.log(newBuf.toString('ascii')); // Prints: '?'</code></pre> <p>Because the Euro (<code>€</code>) sign is not representable in US-ASCII, it is replaced with <code>?</code> in the transcoded <code>Buffer</code>.</p> <p>Note that this is a property on the <code>buffer</code> module returned by <code>require('buffer')</code>, not on the <code>Buffer</code> global or a <code>Buffer</code> instance.</p> <h2>Class: SlowBuffer<span><a class="mark" href="#buffer_class_slowbuffer" id="buffer_class_slowbuffer">#</a></span></h2> <div class="api_metadata"> <span>Deprecated since: v6.0.0</span> </div><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use [`Buffer.allocUnsafeSlow()`] instead.</div><p>Returns an un-pooled <code>Buffer</code>.</p> <p>In order to avoid the garbage collection overhead of creating many individually allocated <code>Buffer</code> instances, by default allocations under 4KB are sliced from a single larger allocated object.</p> <p>In the case where a developer may need to retain a small chunk of memory from a pool for an indeterminate amount of time, it may be appropriate to create an un-pooled <code>Buffer</code> instance using <code>SlowBuffer</code> then copy out the relevant bits.</p> <pre><code class="language-js">// Need to keep around a few small chunks of memory const store = []; socket.on('readable', () => { let data; while (null !== (data = readable.read())) { // Allocate for retained data const sb = SlowBuffer(10); // Copy the data into the new allocation data.copy(sb, 0, 0, 10); store.push(sb); } });</code></pre> <p>Use of <code>SlowBuffer</code> should be used only as a last resort <em>after</em> a developer has observed undue memory retention in their applications.</p> <h3>new SlowBuffer(size)<span><a class="mark" href="#buffer_new_slowbuffer_size" id="buffer_new_slowbuffer_size">#</a></span></h3> <div class="api_metadata"> <span>Deprecated since: v6.0.0</span> </div><div class="api_stability api_stability_0"><a href="documentation.html#documentation_stability_index">Stability: 0</a> - Deprecated: Use [`Buffer.allocUnsafeSlow()`] instead.</div><ul> <li><code>size</code> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The desired length of the new <code>SlowBuffer</code>.</li> </ul> <p>Allocates a new <code>Buffer</code> of <code>size</code> bytes. If <code>size</code> is larger than <a href="#buffer_buffer_constants_max_length"><code>buffer.constants.MAX_LENGTH</code></a> or smaller than 0, <a href="errors.html#ERR_INVALID_OPT_VALUE"><code>ERR_INVALID_OPT_VALUE</code></a> is thrown. A zero-length <code>Buffer</code> is created if <code>size</code> is 0.</p> <p>The underlying memory for <code>SlowBuffer</code> instances is <em>not initialized</em>. The contents of a newly created <code>SlowBuffer</code> are unknown and may contain sensitive data. Use <a href="#buffer_buf_fill_value_offset_end_encoding"><code>buf.fill(0)</code></a> to initialize a <code>SlowBuffer</code> with zeroes.</p> <pre><code class="language-js">const { SlowBuffer } = require('buffer'); const buf = new SlowBuffer(5); console.log(buf); // Prints: (contents may vary): <Buffer 78 e0 82 02 01> buf.fill(0); console.log(buf); // Prints: <Buffer 00 00 00 00 00></code></pre> <h2>Buffer Constants<span><a class="mark" href="#buffer_buffer_constants" id="buffer_buffer_constants">#</a></span></h2> <div class="api_metadata"> <span>Added in: v8.2.0</span> </div><p>Note that <code>buffer.constants</code> is a property on the <code>buffer</code> module returned by <code>require('buffer')</code>, not on the <code>Buffer</code> global or a <code>Buffer</code> instance.</p> <h3>buffer.constants.MAX_LENGTH<span><a class="mark" href="#buffer_buffer_constants_max_length" id="buffer_buffer_constants_max_length">#</a></span></h3> <div class="api_metadata"> <span>Added in: v8.2.0</span> </div><ul> <li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The largest size allowed for a single <code>Buffer</code> instance.</li> </ul> <p>On 32-bit architectures, this value is <code>(2^30)-1</code> (<del>1GB). On 64-bit architectures, this value is <code>(2^31)-1</code> (</del>2GB).</p> <p>This value is also available as <a href="#buffer_buffer_kmaxlength"><code>buffer.kMaxLength</code></a>.</p> <h3>buffer.constants.MAX_STRING_LENGTH<span><a class="mark" href="#buffer_buffer_constants_max_string_length" id="buffer_buffer_constants_max_string_length">#</a></span></h3> <div class="api_metadata"> <span>Added in: v8.2.0</span> </div><ul> <li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type" class="type"><integer></a> The largest length allowed for a single <code>string</code> instance.</li> </ul> <p>Represents the largest <code>length</code> that a <code>string</code> primitive can have, counted in UTF-16 code units.</p> <p>This value may depend on the JS engine that is being used.</p> </div> </div> </div> <script src="assets/sh_main.js"></script> <script src="assets/sh_javascript.min.js"></script> <script>highlight(undefined, undefined, 'pre');</script> </body> </html>
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