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Bun

Node.js module

buffer

The 'node:buffer' module provides a way to handle raw binary data directly in memory. Buffers are instances of the Buffer class, which is a fixed-length sequence of bytes.

The module includes methods to create, read, write, concatenate, and compare buffers. It is fundamental for I/O operations, such as reading files, handling network streams, and interfacing with C++ addons.

Works in Bun

Fully implemented.

  • class Blob

    A Blob encapsulates immutable, raw data that can be safely shared across multiple worker threads.

    • readonly size: number

      The total size of the Blob in bytes.

    • readonly type: string

      The content-type of the Blob.

    • Returns a promise that fulfills with an ArrayBuffer containing a copy of the Blob data.

    • bytes(): Promise<Uint8Array<ArrayBufferLike>>;

      The blob.bytes() method returns the byte of the Blob object as a Promise<Uint8Array>.

      const blob = new Blob(['hello']);
blob.bytes().then((bytes) => {
  console.log(bytes); // Outputs: Uint8Array(5) [ 104, 101, 108, 108, 111 ]
});
    • start?: number,
      end?: number,
      type?: string
      ): Blob;

      Creates and returns a new Blob containing a subset of this Blob objects data. The original Blob is not altered.

      @param start

      The starting index.

      @param end

      The ending index.

      @param type

      The content-type for the new Blob

    • Returns a new ReadableStream that allows the content of the Blob to be read.

    • text(): Promise<string>;

      Returns a promise that fulfills with the contents of the Blob decoded as a UTF-8 string.

  • class File

    A File provides information about files.

    • readonly lastModified: number

      The last modified date of the File.

    • readonly name: string

      The name of the File.

    • readonly size: number

      The total size of the Blob in bytes.

    • readonly type: string

      The content-type of the Blob.

    • Returns a promise that fulfills with an ArrayBuffer containing a copy of the Blob data.

    • bytes(): Promise<Uint8Array<ArrayBufferLike>>;

      The blob.bytes() method returns the byte of the Blob object as a Promise<Uint8Array>.

      const blob = new Blob(['hello']);
blob.bytes().then((bytes) => {
  console.log(bytes); // Outputs: Uint8Array(5) [ 104, 101, 108, 108, 111 ]
});
    • start?: number,
      end?: number,
      type?: string
      ): Blob;

      Creates and returns a new Blob containing a subset of this Blob objects data. The original Blob is not altered.

      @param start

      The starting index.

      @param end

      The ending index.

      @param type

      The content-type for the new Blob

    • Returns a new ReadableStream that allows the content of the Blob to be read.

    • text(): Promise<string>;

      Returns a promise that fulfills with the contents of the Blob decoded as a UTF-8 string.

  • const Buffer: BufferConstructor
  • const constants: { MAX_LENGTH: number; MAX_STRING_LENGTH: number }
  • const INSPECT_MAX_BYTES: number
  • const kMaxLength: number
  • const kStringMaxLength: number
  • function atob(
    data: string
    ): string;

    Decodes a string of Base64-encoded data into bytes, and encodes those bytes into a string using Latin-1 (ISO-8859-1).

    The data may be any JavaScript-value that can be coerced into a string.

    This function is only provided for compatibility with legacy web platform APIs and should never be used in new code, because they use strings to represent binary data and predate the introduction of typed arrays in JavaScript. For code running using Node.js APIs, converting between base64-encoded strings and binary data should be performed using Buffer.from(str, 'base64') and buf.toString('base64').

    @param data

    The Base64-encoded input string.

  • function btoa(
    data: string
    ): string;

    Decodes a string into bytes using Latin-1 (ISO-8859), and encodes those bytes into a string using Base64.

    The data may be any JavaScript-value that can be coerced into a string.

    This function is only provided for compatibility with legacy web platform APIs and should never be used in new code, because they use strings to represent binary data and predate the introduction of typed arrays in JavaScript. For code running using Node.js APIs, converting between base64-encoded strings and binary data should be performed using Buffer.from(str, 'base64') and buf.toString('base64').

    @param data

    An ASCII (Latin1) string.

  • function isAscii(
    input: ArrayBuffer | Buffer<ArrayBufferLike> | TypedArray<ArrayBufferLike>
    ): boolean;

    This function returns true if input contains only valid ASCII-encoded data, including the case in which input is empty.

    Throws if the input is a detached array buffer.

    @param input

    The input to validate.

  • function isUtf8(
    input: ArrayBuffer | Buffer<ArrayBufferLike> | TypedArray<ArrayBufferLike>
    ): boolean;

    This function returns true if input contains only valid UTF-8-encoded data, including the case in which input is empty.

    Throws if the input is a detached array buffer.

    @param input

    The input to validate.

  • id: string
    ): undefined | Blob;

    Resolves a 'blob:nodedata:...' an associated Blob object registered using a prior call to URL.createObjectURL().

    @param id

    A 'blob:nodedata:... URL string returned by a prior call to URL.createObjectURL().

  • function transcode(
    source: Uint8Array,
    fromEnc: TranscodeEncoding,
    toEnc: TranscodeEncoding
    ): Buffer;

    Re-encodes the given Buffer or Uint8Array instance from one character encoding to another. Returns a new Buffer instance.

    Throws if the fromEnc or toEnc specify invalid character encodings or if conversion from fromEnc to toEnc is not permitted.

    Encodings supported by buffer.transcode() are: 'ascii', 'utf8', 'utf16le', 'ucs2', 'latin1', and 'binary'.

    The transcoding process will use substitution characters if a given byte sequence cannot be adequately represented in the target encoding. For instance:

    import { Buffer, transcode } from 'node:buffer';

const newBuf = transcode(Buffer.from('€'), 'utf8', 'ascii');
console.log(newBuf.toString('ascii'));
// Prints: '?'

    Because the Euro (€) sign is not representable in US-ASCII, it is replaced with ? in the transcoded Buffer.

    @param source

    A Buffer or Uint8Array instance.

    @param fromEnc

    The current encoding.

    @param toEnc

    To target encoding.

Type definitions

  • interface BlobOptions

    • endings?: 'transparent' | 'native'

      One of either 'transparent' or 'native'. When set to 'native', line endings in string source parts will be converted to the platform native line-ending as specified by import { EOL } from 'node:os'.

    • type?: string

      The Blob content-type. The intent is for type to convey the MIME media type of the data, however no validation of the type format is performed.

  • interface Buffer<TArrayBuffer extends ArrayBufferLike = ArrayBufferLike>

    A typed array of 8-bit unsigned integer values. The contents are initialized to 0. If the requested number of bytes could not be allocated an exception is raised.

    • readonly [Symbol.toStringTag]: 'Uint8Array'
    • readonly buffer: TArrayBuffer

      The ArrayBuffer instance referenced by the array.

    • readonly byteLength: number

      The length in bytes of the array.

    • readonly byteOffset: number

      The offset in bytes of the array.

    • readonly BYTES_PER_ELEMENT: number

      The size in bytes of each element in the array.

    • readonly length: number

      The length of the array.

    • [Symbol.iterator](): ArrayIterator<number>;
    • index: number
      ): undefined | number;

      Returns the item located at the specified index.

      @param index

      The zero-based index of the desired code unit. A negative index will count back from the last item.

    • target: Uint8Array,
      targetStart?: number,
      targetEnd?: number,
      sourceStart?: number,
      sourceEnd?: number
      ): -1 | 0 | 1;

      Compares buf with target and returns a number indicating whether bufcomes before, after, or is the same as target in sort order. Comparison is based on the actual sequence of bytes in each Buffer.

      • 0 is returned if target is the same as buf
      • 1 is returned if target should come beforebuf when sorted.
      • -1 is returned if target should come afterbuf when sorted.
      import { Buffer } from 'node:buffer';

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].)

      The optional targetStart, targetEnd, sourceStart, and sourceEnd arguments can be used to limit the comparison to specific ranges within target and buf respectively.

      import { Buffer } from 'node:buffer';

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

      ERR_OUT_OF_RANGE is thrown if targetStart < 0, sourceStart < 0, targetEnd > target.byteLength, or sourceEnd > source.byteLength.

      @param target

      A Buffer or Uint8Array with which to compare buf.

      @param targetStart

      The offset within target at which to begin comparison.

      @param targetEnd

      The offset within target at which to end comparison (not inclusive).

      @param sourceStart

      The offset within buf at which to begin comparison.

      @param sourceEnd

      The offset within buf at which to end comparison (not inclusive).

    • target: Uint8Array,
      targetStart?: number,
      sourceStart?: number,
      sourceEnd?: number
      ): number;

      Copies data from a region of buf to a region in target, even if the targetmemory region overlaps with buf.

      TypedArray.prototype.set() performs the same operation, and is available for all TypedArrays, including Node.js Buffers, although it takes different function arguments.

      import { Buffer } from 'node:buffer';

// 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);
// This is equivalent to:
// buf2.set(buf1.subarray(16, 20), 8);

console.log(buf2.toString('ascii', 0, 25));
// Prints: !!!!!!!!qrst!!!!!!!!!!!!!

      import { Buffer } from 'node:buffer';

// 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
      @param target

      A Buffer or Uint8Array to copy into.

      @param targetStart

      The offset within target at which to begin writing.

      @param sourceStart

      The offset within buf from which to begin copying.

      @param sourceEnd

      The offset within buf at which to stop copying (not inclusive).

      @returns

      The number of bytes copied.

    • target: number,
      start: number,
      end?: number
      ): this;

      Returns the this object after copying a section of the array identified by start and end to the same array starting at position target

      @param target

      If target is negative, it is treated as length+target where length is the length of the array.

      @param start

      If start is negative, it is treated as length+start. If end is negative, it is treated as length+end.

      @param end

      If not specified, length of the this object is used as its default value.

    • entries(): ArrayIterator<[number, number]>;

      Returns an array of key, value pairs for every entry in the array

    • otherBuffer: Uint8Array
      ): boolean;

      Returns true if both buf and otherBuffer have exactly the same bytes,false otherwise. Equivalent to buf.compare(otherBuffer) === 0.

      import { Buffer } from 'node:buffer';

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
      @param otherBuffer

      A Buffer or Uint8Array with which to compare buf.

    • predicate: (value: number, index: number, array: this) => unknown,
      thisArg?: any
      ): boolean;

      Determines whether all the members of an array satisfy the specified test.

      @param predicate

      A function that accepts up to three arguments. The every method calls the predicate function for each element in the array until the predicate returns a value which is coercible to the Boolean value false, or until the end of the array.

      @param thisArg

      An object to which the this keyword can refer in the predicate function. If thisArg is omitted, undefined is used as the this value.

    • value: string | number | Uint8Array<ArrayBufferLike>,
      offset?: number,
      end?: number,
      encoding?: BufferEncoding
      ): this;

      Fills buf with the specified value. If the offset and end are not given, the entire buf will be filled:

      import { Buffer } from 'node:buffer';

// Fill a `Buffer` with the ASCII character 'h'.

const b = Buffer.allocUnsafe(50).fill('h');

console.log(b.toString());
// Prints: hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh

// Fill a buffer with empty string
const c = Buffer.allocUnsafe(5).fill('');

console.log(c.fill(''));
// Prints: <Buffer 00 00 00 00 00>

      value is coerced to a uint32 value if it is not a string, Buffer, or integer. If the resulting integer is greater than 255 (decimal), buf will be filled with value &#x26; 255.

      If the final write of a fill() operation falls on a multi-byte character, then only the bytes of that character that fit into buf are written:

      import { Buffer } from 'node:buffer';

// Fill a `Buffer` with character that takes up two bytes in UTF-8.

console.log(Buffer.allocUnsafe(5).fill('\u0222'));
// Prints: <Buffer c8 a2 c8 a2 c8>

      If value contains invalid characters, it is truncated; if no valid fill data remains, an exception is thrown:

      import { Buffer } from 'node:buffer';

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.
      @param value

      The value with which to fill buf. Empty value (string, Uint8Array, Buffer) is coerced to 0.

      @param offset

      Number of bytes to skip before starting to fill buf.

      @param end

      Where to stop filling buf (not inclusive).

      @param encoding

      The encoding for value if value is a string.

      @returns

      A reference to buf.

    • predicate: (value: number, index: number, array: this) => any,
      thisArg?: any

      Returns the elements of an array that meet the condition specified in a callback function.

      @param predicate

      A function that accepts up to three arguments. The filter method calls the predicate function one time for each element in the array.

      @param thisArg

      An object to which the this keyword can refer in the predicate function. If thisArg is omitted, undefined is used as the this value.

    • predicate: (value: number, index: number, obj: this) => boolean,
      thisArg?: any
      ): undefined | number;

      Returns the value of the first element in the array where predicate is true, and undefined otherwise.

      @param predicate

      find calls predicate once for each element of the array, in ascending order, until it finds one where predicate returns true. If such an element is found, find immediately returns that element value. Otherwise, find returns undefined.

      @param thisArg

      If provided, it will be used as the this value for each invocation of predicate. If it is not provided, undefined is used instead.

    • predicate: (value: number, index: number, obj: this) => boolean,
      thisArg?: any
      ): number;

      Returns the index of the first element in the array where predicate is true, and -1 otherwise.

      @param predicate

      find calls predicate once for each element of the array, in ascending order, until it finds one where predicate returns true. If such an element is found, findIndex immediately returns that element index. Otherwise, findIndex returns -1.

      @param thisArg

      If provided, it will be used as the this value for each invocation of predicate. If it is not provided, undefined is used instead.

    • findLast<S extends number>(
      predicate: (value: number, index: number, array: this) => value is S,
      thisArg?: any
      ): undefined | S;

      Returns the value of the last element in the array where predicate is true, and undefined otherwise.

      @param predicate

      findLast calls predicate once for each element of the array, in descending order, until it finds one where predicate returns true. If such an element is found, findLast immediately returns that element value. Otherwise, findLast returns undefined.

      @param thisArg

      If provided, it will be used as the this value for each invocation of predicate. If it is not provided, undefined is used instead.

      predicate: (value: number, index: number, array: this) => unknown,
      thisArg?: any
      ): undefined | number;
    • predicate: (value: number, index: number, array: this) => unknown,
      thisArg?: any
      ): number;

      Returns the index of the last element in the array where predicate is true, and -1 otherwise.

      @param predicate

      findLastIndex calls predicate once for each element of the array, in descending order, until it finds one where predicate returns true. If such an element is found, findLastIndex immediately returns that element index. Otherwise, findLastIndex returns -1.

      @param thisArg

      If provided, it will be used as the this value for each invocation of predicate. If it is not provided, undefined is used instead.

    • callbackfn: (value: number, index: number, array: this) => void,
      thisArg?: any
      ): void;

      Performs the specified action for each element in an array.

      @param callbackfn

      A function that accepts up to three arguments. forEach calls the callbackfn function one time for each element in the array.

      @param thisArg

      An object to which the this keyword can refer in the callbackfn function. If thisArg is omitted, undefined is used as the this value.

    • value: string | number | Buffer<ArrayBufferLike>,
      byteOffset?: number,
      encoding?: BufferEncoding
      ): boolean;

      Equivalent to buf.indexOf() !== -1.

      import { Buffer } from 'node:buffer';

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
      @param value

      What to search for.

      @param byteOffset

      Where to begin searching in buf. If negative, then offset is calculated from the end of buf.

      @param encoding

      If value is a string, this is its encoding.

      @returns

      true if value was found in buf, false otherwise.

    • value: string | number | Uint8Array<ArrayBufferLike>,
      byteOffset?: number,
      encoding?: BufferEncoding
      ): number;

      If value is:

      • a string, value is interpreted according to the character encoding in encoding.
      • a Buffer or Uint8Array, value will be used in its entirety. To compare a partial Buffer, use buf.subarray.
      • a number, value will be interpreted as an unsigned 8-bit integer value between 0 and 255.
      import { Buffer } from 'node:buffer';

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

      If value is not a string, number, or Buffer, this method will throw a TypeError. If value is a number, it will be coerced to a valid byte value, an integer between 0 and 255.

      If byteOffset is not a number, it will be coerced to a number. If the result of coercion is NaN or 0, then the entire buffer will be searched. This behavior matches String.prototype.indexOf().

      import { Buffer } from 'node:buffer';

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', []));

      If value is an empty string or empty Buffer and byteOffset is less than buf.length, byteOffset will be returned. If value is empty andbyteOffset is at least buf.length, buf.length will be returned.

      @param value

      What to search for.

      @param byteOffset

      Where to begin searching in buf. If negative, then offset is calculated from the end of buf.

      @param encoding

      If value is a string, this is the encoding used to determine the binary representation of the string that will be searched for in buf.

      @returns

      The index of the first occurrence of value in buf, or -1 if buf does not contain value.

    • separator?: string
      ): string;

      Adds all the elements of an array separated by the specified separator string.

      @param separator

      A string used to separate one element of an array from the next in the resulting String. If omitted, the array elements are separated with a comma.

    • keys(): ArrayIterator<number>;

      Returns an list of keys in the array

    • value: string | number | Uint8Array<ArrayBufferLike>,
      byteOffset?: number,
      encoding?: BufferEncoding
      ): number;

      Identical to buf.indexOf(), except the last occurrence of value is found rather than the first occurrence.

      import { Buffer } from 'node:buffer';

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

      If value is not a string, number, or Buffer, this method will throw a TypeError. If value is a number, it will be coerced to a valid byte value, an integer between 0 and 255.

      If byteOffset is not a number, it will be coerced to a number. Any arguments that coerce to NaN, like {} or undefined, will search the whole buffer. This behavior matches String.prototype.lastIndexOf().

      import { Buffer } from 'node:buffer';

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', []));

      If value is an empty string or empty Buffer, byteOffset will be returned.

      @param value

      What to search for.

      @param byteOffset

      Where to begin searching in buf. If negative, then offset is calculated from the end of buf.

      @param encoding

      If value is a string, this is the encoding used to determine the binary representation of the string that will be searched for in buf.

      @returns

      The index of the last occurrence of value in buf, or -1 if buf does not contain value.

    • callbackfn: (value: number, index: number, array: this) => number,
      thisArg?: any

      Calls a defined callback function on each element of an array, and returns an array that contains the results.

      @param callbackfn

      A function that accepts up to three arguments. The map method calls the callbackfn function one time for each element in the array.

      @param thisArg

      An object to which the this keyword can refer in the callbackfn function. If thisArg is omitted, undefined is used as the this value.

    • offset?: number
      ): bigint;

      Reads a signed, big-endian 64-bit integer from buf at the specified offset.

      Integers read from a Buffer are interpreted as two's complement signed values.

      @param offset

      Number of bytes to skip before starting to read. Must satisfy: 0 <= offset <= buf.length - 8.

    • offset?: number
      ): bigint;

      Reads a signed, little-endian 64-bit integer from buf at the specifiedoffset.

      Integers read from a Buffer are interpreted as two's complement signed values.

      @param offset

      Number of bytes to skip before starting to read. Must satisfy: 0 <= offset <= buf.length - 8.

    • offset?: number
      ): bigint;
    • offset?: number
      ): bigint;

      Reads an unsigned, big-endian 64-bit integer from buf at the specifiedoffset.

      This function is also available under the readBigUint64BE alias.

      import { Buffer } from 'node:buffer';

const buf = Buffer.from([0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff]);

console.log(buf.readBigUInt64BE(0));
// Prints: 4294967295n
      @param offset

      Number of bytes to skip before starting to read. Must satisfy: 0 <= offset <= buf.length - 8.

    • offset?: number
      ): bigint;
    • offset?: number
      ): bigint;

      Reads an unsigned, little-endian 64-bit integer from buf at the specifiedoffset.

      This function is also available under the readBigUint64LE alias.

      import { Buffer } from 'node:buffer';

const buf = Buffer.from([0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff]);

console.log(buf.readBigUInt64LE(0));
// Prints: 18446744069414584320n
      @param offset

      Number of bytes to skip before starting to read. Must satisfy: 0 <= offset <= buf.length - 8.

    • offset?: number
      ): number;

      Reads a 64-bit, big-endian double from buf at the specified offset.

      import { Buffer } from 'node:buffer';

const buf = Buffer.from([1, 2, 3, 4, 5, 6, 7, 8]);

console.log(buf.readDoubleBE(0));
// Prints: 8.20788039913184e-304
      @param offset

      Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 8.

    • offset?: number
      ): number;

      Reads a 64-bit, little-endian double from buf at the specified offset.

      import { Buffer } from 'node:buffer';

const buf = Buffer.from([1, 2, 3, 4, 5, 6, 7, 8]);

console.log(buf.readDoubleLE(0));
// Prints: 5.447603722011605e-270
console.log(buf.readDoubleLE(1));
// Throws ERR_OUT_OF_RANGE.
      @param offset

      Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 8.

    • offset?: number
      ): number;

      Reads a 32-bit, big-endian float from buf at the specified offset.

      import { Buffer } from 'node:buffer';

const buf = Buffer.from([1, 2, 3, 4]);

console.log(buf.readFloatBE(0));
// Prints: 2.387939260590663e-38
      @param offset

      Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 4.

    • offset?: number
      ): number;

      Reads a 32-bit, little-endian float from buf at the specified offset.

      import { Buffer } from 'node:buffer';

const buf = Buffer.from([1, 2, 3, 4]);

console.log(buf.readFloatLE(0));
// Prints: 1.539989614439558e-36
console.log(buf.readFloatLE(1));
// Throws ERR_OUT_OF_RANGE.
      @param offset

      Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 4.

    • offset?: number
      ): number;

      Reads a signed, big-endian 16-bit integer from buf at the specified offset.

      Integers read from a Buffer are interpreted as two's complement signed values.

      import { Buffer } from 'node:buffer';

const buf = Buffer.from([0, 5]);

console.log(buf.readInt16BE(0));
// Prints: 5
      @param offset

      Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 2.

    • offset?: number
      ): number;

      Reads a signed, little-endian 16-bit integer from buf at the specifiedoffset.

      Integers read from a Buffer are interpreted as two's complement signed values.

      import { Buffer } from 'node:buffer';

const buf = Buffer.from([0, 5]);

console.log(buf.readInt16LE(0));
// Prints: 1280
console.log(buf.readInt16LE(1));
// Throws ERR_OUT_OF_RANGE.
      @param offset

      Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 2.

    • offset?: number
      ): number;

      Reads a signed, big-endian 32-bit integer from buf at the specified offset.

      Integers read from a Buffer are interpreted as two's complement signed values.

      import { Buffer } from 'node:buffer';

const buf = Buffer.from([0, 0, 0, 5]);

console.log(buf.readInt32BE(0));
// Prints: 5
      @param offset

      Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 4.

    • offset?: number
      ): number;

      Reads a signed, little-endian 32-bit integer from buf at the specifiedoffset.

      Integers read from a Buffer are interpreted as two's complement signed values.

      import { Buffer } from 'node:buffer';

const buf = Buffer.from([0, 0, 0, 5]);

console.log(buf.readInt32LE(0));
// Prints: 83886080
console.log(buf.readInt32LE(1));
// Throws ERR_OUT_OF_RANGE.
      @param offset

      Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 4.

    • offset?: number
      ): number;

      Reads a signed 8-bit integer from buf at the specified offset.

      Integers read from a Buffer are interpreted as two's complement signed values.

      import { Buffer } from 'node:buffer';

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.
      @param offset

      Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 1.

    • offset: number,
      byteLength: number
      ): number;

      Reads byteLength number of bytes from buf at the specified offset and interprets the result as a big-endian, two's complement signed value supporting up to 48 bits of accuracy.

      import { Buffer } from 'node:buffer';

const buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);

console.log(buf.readIntBE(0, 6).toString(16));
// Prints: 1234567890ab
console.log(buf.readIntBE(1, 6).toString(16));
// Throws ERR_OUT_OF_RANGE.
console.log(buf.readIntBE(1, 0).toString(16));
// Throws ERR_OUT_OF_RANGE.
      @param offset

      Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - byteLength.

      @param byteLength

      Number of bytes to read. Must satisfy 0 < byteLength <= 6.

    • offset: number,
      byteLength: number
      ): number;

      Reads byteLength number of bytes from buf at the specified offset and interprets the result as a little-endian, two's complement signed value supporting up to 48 bits of accuracy.

      import { Buffer } from 'node:buffer';

const buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);

console.log(buf.readIntLE(0, 6).toString(16));
// Prints: -546f87a9cbee
      @param offset

      Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - byteLength.

      @param byteLength

      Number of bytes to read. Must satisfy 0 < byteLength <= 6.

    • offset?: number
      ): number;
    • offset?: number
      ): number;

      Reads an unsigned, big-endian 16-bit integer from buf at the specifiedoffset.

      This function is also available under the readUint16BE alias.

      import { Buffer } from 'node:buffer';

const buf = Buffer.from([0x12, 0x34, 0x56]);

console.log(buf.readUInt16BE(0).toString(16));
// Prints: 1234
console.log(buf.readUInt16BE(1).toString(16));
// Prints: 3456
      @param offset

      Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 2.

    • offset?: number
      ): number;
    • offset?: number
      ): number;

      Reads an unsigned, little-endian 16-bit integer from buf at the specified offset.

      This function is also available under the readUint16LE alias.

      import { Buffer } from 'node:buffer';

const buf = Buffer.from([0x12, 0x34, 0x56]);

console.log(buf.readUInt16LE(0).toString(16));
// Prints: 3412
console.log(buf.readUInt16LE(1).toString(16));
// Prints: 5634
console.log(buf.readUInt16LE(2).toString(16));
// Throws ERR_OUT_OF_RANGE.
      @param offset

      Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 2.

    • offset?: number
      ): number;
    • offset?: number
      ): number;

      Reads an unsigned, big-endian 32-bit integer from buf at the specifiedoffset.

      This function is also available under the readUint32BE alias.

      import { Buffer } from 'node:buffer';

const buf = Buffer.from([0x12, 0x34, 0x56, 0x78]);

console.log(buf.readUInt32BE(0).toString(16));
// Prints: 12345678
      @param offset

      Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 4.

    • offset?: number
      ): number;
    • offset?: number
      ): number;

      Reads an unsigned, little-endian 32-bit integer from buf at the specifiedoffset.

      This function is also available under the readUint32LE alias.

      import { Buffer } from 'node:buffer';

const buf = Buffer.from([0x12, 0x34, 0x56, 0x78]);

console.log(buf.readUInt32LE(0).toString(16));
// Prints: 78563412
console.log(buf.readUInt32LE(1).toString(16));
// Throws ERR_OUT_OF_RANGE.
      @param offset

      Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 4.

    • offset?: number
      ): number;
    • offset?: number
      ): number;

      Reads an unsigned 8-bit integer from buf at the specified offset.

      This function is also available under the readUint8 alias.

      import { Buffer } from 'node:buffer';

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.
      @param offset

      Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 1.

    • offset: number,
      byteLength: number
      ): number;
    • offset: number,
      byteLength: number
      ): number;

      Reads byteLength number of bytes from buf at the specified offset and interprets the result as an unsigned big-endian integer supporting up to 48 bits of accuracy.

      This function is also available under the readUintBE alias.

      import { Buffer } from 'node:buffer';

const buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);

console.log(buf.readUIntBE(0, 6).toString(16));
// Prints: 1234567890ab
console.log(buf.readUIntBE(1, 6).toString(16));
// Throws ERR_OUT_OF_RANGE.
      @param offset

      Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - byteLength.

      @param byteLength

      Number of bytes to read. Must satisfy 0 < byteLength <= 6.

    • offset: number,
      byteLength: number
      ): number;
    • offset: number,
      byteLength: number
      ): number;

      Reads byteLength number of bytes from buf at the specified offset and interprets the result as an unsigned, little-endian integer supporting up to 48 bits of accuracy.

      This function is also available under the readUintLE alias.

      import { Buffer } from 'node:buffer';

const buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);

console.log(buf.readUIntLE(0, 6).toString(16));
// Prints: ab9078563412
      @param offset

      Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - byteLength.

      @param byteLength

      Number of bytes to read. Must satisfy 0 < byteLength <= 6.

    • callbackfn: (previousValue: number, currentValue: number, currentIndex: number, array: this) => number
      ): number;

      Calls the specified callback function for all the elements in an array. The return value of the callback function is the accumulated result, and is provided as an argument in the next call to the callback function.

      @param callbackfn

      A function that accepts up to four arguments. The reduce method calls the callbackfn function one time for each element in the array.

      callbackfn: (previousValue: number, currentValue: number, currentIndex: number, array: this) => number,
      initialValue: number
      ): number;
      reduce<U>(
      callbackfn: (previousValue: U, currentValue: number, currentIndex: number, array: this) => U,
      initialValue: U
      ): U;

      Calls the specified callback function for all the elements in an array. The return value of the callback function is the accumulated result, and is provided as an argument in the next call to the callback function.

      @param callbackfn

      A function that accepts up to four arguments. The reduce method calls the callbackfn function one time for each element in the array.

      @param initialValue

      If initialValue is specified, it is used as the initial value to start the accumulation. The first call to the callbackfn function provides this value as an argument instead of an array value.

    • callbackfn: (previousValue: number, currentValue: number, currentIndex: number, array: this) => number
      ): number;

      Calls the specified callback function for all the elements in an array, in descending order. The return value of the callback function is the accumulated result, and is provided as an argument in the next call to the callback function.

      @param callbackfn

      A function that accepts up to four arguments. The reduceRight method calls the callbackfn function one time for each element in the array.

      callbackfn: (previousValue: number, currentValue: number, currentIndex: number, array: this) => number,
      initialValue: number
      ): number;
      callbackfn: (previousValue: U, currentValue: number, currentIndex: number, array: this) => U,
      initialValue: U
      ): U;

      Calls the specified callback function for all the elements in an array, in descending order. The return value of the callback function is the accumulated result, and is provided as an argument in the next call to the callback function.

      @param callbackfn

      A function that accepts up to four arguments. The reduceRight method calls the callbackfn function one time for each element in the array.

      @param initialValue

      If initialValue is specified, it is used as the initial value to start the accumulation. The first call to the callbackfn function provides this value as an argument instead of an array value.

    • reverse(): this;

      Reverses the elements in an Array.

    • array: ArrayLike<number>,
      offset?: number
      ): void;

      Sets a value or an array of values.

      @param array

      A typed or untyped array of values to set.

      @param offset

      The index in the current array at which the values are to be written.

    • base64: string,
      offset?: number
      ): { read: number; written: number };

      Set the contents of the Uint8Array from a base64 encoded string

      @param base64

      The base64 encoded string to decode into the array

      @param offset

      Optional starting index to begin setting the decoded bytes (default: 0)

    • hex: string
      ): { read: number; written: number };

      Set the contents of the Uint8Array from a hex encoded string

      @param hex

      The hex encoded string to decode into the array. The string must have an even number of characters, be valid hexadecimal characters and contain no whitespace.

    • predicate: (value: number, index: number, array: this) => unknown,
      thisArg?: any
      ): boolean;

      Determines whether the specified callback function returns true for any element of an array.

      @param predicate

      A function that accepts up to three arguments. The some method calls the predicate function for each element in the array until the predicate returns a value which is coercible to the Boolean value true, or until the end of the array.

      @param thisArg

      An object to which the this keyword can refer in the predicate function. If thisArg is omitted, undefined is used as the this value.

    • compareFn?: (a: number, b: number) => number
      ): this;

      Sorts an array.

      @param compareFn

      Function used to determine the order of the elements. It is expected to return a negative value if first argument is less than second argument, zero if they're equal and a positive value otherwise. If omitted, the elements are sorted in ascending order.

      [11,2,22,1].sort((a, b) => a - b)
    • start?: number,
      end?: number
      ): Buffer<TArrayBuffer>;

      Returns a new Buffer that references the same memory as the original, but offset and cropped by the start and end indices.

      Specifying end greater than buf.length will return the same result as that of end equal to buf.length.

      This method is inherited from TypedArray.prototype.subarray().

      Modifying the new Buffer slice will modify the memory in the original Bufferbecause the allocated memory of the two objects overlap.

      import { Buffer } from 'node:buffer';

// 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.subarray(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

      Specifying negative indexes causes the slice to be generated relative to the end of buf rather than the beginning.

      import { Buffer } from 'node:buffer';

const buf = Buffer.from('buffer');

console.log(buf.subarray(-6, -1).toString());
// Prints: buffe
// (Equivalent to buf.subarray(0, 5).)

console.log(buf.subarray(-6, -2).toString());
// Prints: buff
// (Equivalent to buf.subarray(0, 4).)

console.log(buf.subarray(-5, -2).toString());
// Prints: uff
// (Equivalent to buf.subarray(1, 4).)
      @param start

      Where the new Buffer will start.

      @param end

      Where the new Buffer will end (not inclusive).

    • swap16(): this;

      Interprets buf as an array of unsigned 16-bit integers and swaps the byte order in-place. Throws ERR_INVALID_BUFFER_SIZE if buf.length is not a multiple of 2.

      import { Buffer } from 'node:buffer';

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.

      One convenient use of buf.swap16() is to perform a fast in-place conversion between UTF-16 little-endian and UTF-16 big-endian:

      import { Buffer } from 'node:buffer';

const buf = Buffer.from('This is little-endian UTF-16', 'utf16le');
buf.swap16(); // Convert to big-endian UTF-16 text.
      @returns

      A reference to buf.

    • swap32(): this;

      Interprets buf as an array of unsigned 32-bit integers and swaps the byte order in-place. Throws ERR_INVALID_BUFFER_SIZE if buf.length is not a multiple of 4.

      import { Buffer } from 'node:buffer';

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.
      @returns

      A reference to buf.

    • swap64(): this;

      Interprets buf as an array of 64-bit numbers and swaps byte order in-place. Throws ERR_INVALID_BUFFER_SIZE if buf.length is not a multiple of 8.

      import { Buffer } from 'node:buffer';

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.
      @returns

      A reference to buf.

    • options?: { alphabet: 'base64' | 'base64url'; omitPadding: boolean }
      ): string;

      Convert the Uint8Array to a base64 encoded string

      @returns

      The base64 encoded string representation of the Uint8Array

    • toHex(): string;

      Convert the Uint8Array to a hex encoded string

      @returns

      The hex encoded string representation of the Uint8Array

    • toJSON(): { data: number[]; type: 'Buffer' };

      Returns a JSON representation of buf. JSON.stringify() implicitly calls this function when stringifying a Buffer instance.

      Buffer.from() accepts objects in the format returned from this method. In particular, Buffer.from(buf.toJSON()) works like Buffer.from(buf).

      import { Buffer } from 'node:buffer';

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 &#x26;&#x26; value.type === 'Buffer' ?
    Buffer.from(value) :
    value;
});

console.log(copy);
// Prints: <Buffer 01 02 03 04 05>
    • toLocaleString(): string;

      Converts a number to a string by using the current locale.

      locales: string | string[],
      options?: NumberFormatOptions
      ): string;

    • Copies the array and returns the copy with the elements in reverse order.

    • compareFn?: (a: number, b: number) => number

      Copies and sorts the array.

      @param compareFn

      Function used to determine the order of the elements. It is expected to return a negative value if the first argument is less than the second argument, zero if they're equal, and a positive value otherwise. If omitted, the elements are sorted in ascending order.

      const myNums = Uint8Array.from([11, 2, 22, 1]);
myNums.toSorted((a, b) => a - b) // Uint8Array(4) [1, 2, 11, 22]
    • encoding?: BufferEncoding,
      start?: number,
      end?: number
      ): string;

      Decodes buf to a string according to the specified character encoding inencoding. start and end may be passed to decode only a subset of buf.

      If encoding is 'utf8' and a byte sequence in the input is not valid UTF-8, then each invalid byte is replaced with the replacement character U+FFFD.

      The maximum length of a string instance (in UTF-16 code units) is available as constants.MAX_STRING_LENGTH.

      import { Buffer } from 'node: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;
}

console.log(buf1.toString('utf8'));
// Prints: abcdefghijklmnopqrstuvwxyz
console.log(buf1.toString('utf8', 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
      @param encoding

      The character encoding to use.

      @param start

      The byte offset to start decoding at.

      @param end

      The byte offset to stop decoding at (not inclusive).

    • valueOf(): this;

      Returns the primitive value of the specified object.

    • values(): ArrayIterator<number>;

      Returns an list of values in the array

    • index: number,
      value: number

      Copies the array and inserts the given number at the provided index.

      @param index

      The index of the value to overwrite. If the index is negative, then it replaces from the end of the array.

      @param value

      The value to insert into the copied array.

      @returns

      A copy of the original array with the inserted value.

    • string: string,
      encoding?: BufferEncoding
      ): number;

      Writes string to buf at offset according to the character encoding inencoding. The length parameter is the number of bytes to write. If buf did not contain enough space to fit the entire string, only part of string will be written. However, partially encoded characters will not be written.

      import { Buffer } from 'node:buffer';

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

const buffer = Buffer.alloc(10);

const length = buffer.write('abcd', 8);

console.log(`${length} bytes: ${buffer.toString('utf8', 8, 10)}`);
// Prints: 2 bytes : ab
      @param string

      String to write to buf.

      @param encoding

      The character encoding of string.

      @returns

      Number of bytes written.

      string: string,
      offset: number,
      encoding?: BufferEncoding
      ): number;
      string: string,
      offset: number,
      length: number,
      encoding?: BufferEncoding
      ): number;
    • value: bigint,
      offset?: number
      ): number;

      Writes value to buf at the specified offset as big-endian.

      value is interpreted and written as a two's complement signed integer.

      import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(8);

buf.writeBigInt64BE(0x0102030405060708n, 0);

console.log(buf);
// Prints: <Buffer 01 02 03 04 05 06 07 08>
      @param value

      Number to be written to buf.

      @param offset

      Number of bytes to skip before starting to write. Must satisfy: 0 <= offset <= buf.length - 8.

      @returns

      offset plus the number of bytes written.

    • value: bigint,
      offset?: number
      ): number;

      Writes value to buf at the specified offset as little-endian.

      value is interpreted and written as a two's complement signed integer.

      import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(8);

buf.writeBigInt64LE(0x0102030405060708n, 0);

console.log(buf);
// Prints: <Buffer 08 07 06 05 04 03 02 01>
      @param value

      Number to be written to buf.

      @param offset

      Number of bytes to skip before starting to write. Must satisfy: 0 <= offset <= buf.length - 8.

      @returns

      offset plus the number of bytes written.

    • value: bigint,
      offset?: number
      ): number;
    • value: bigint,
      offset?: number
      ): number;

      Writes value to buf at the specified offset as big-endian.

      This function is also available under the writeBigUint64BE alias.

      import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(8);

buf.writeBigUInt64BE(0xdecafafecacefaden, 0);

console.log(buf);
// Prints: <Buffer de ca fa fe ca ce fa de>
      @param value

      Number to be written to buf.

      @param offset

      Number of bytes to skip before starting to write. Must satisfy: 0 <= offset <= buf.length - 8.

      @returns

      offset plus the number of bytes written.

    • value: bigint,
      offset?: number
      ): number;
    • value: bigint,
      offset?: number
      ): number;

      Writes value to buf at the specified offset as little-endian

      import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(8);

buf.writeBigUInt64LE(0xdecafafecacefaden, 0);

console.log(buf);
// Prints: <Buffer de fa ce ca fe fa ca de>

      This function is also available under the writeBigUint64LE alias.

      @param value

      Number to be written to buf.

      @param offset

      Number of bytes to skip before starting to write. Must satisfy: 0 <= offset <= buf.length - 8.

      @returns

      offset plus the number of bytes written.

    • value: number,
      offset?: number
      ): number;

      Writes value to buf at the specified offset as big-endian. The value must be a JavaScript number. Behavior is undefined when value is anything other than a JavaScript number.

      import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(8);

buf.writeDoubleBE(123.456, 0);

console.log(buf);
// Prints: <Buffer 40 5e dd 2f 1a 9f be 77>
      @param value

      Number to be written to buf.

      @param offset

      Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 8.

      @returns

      offset plus the number of bytes written.

    • value: number,
      offset?: number
      ): number;

      Writes value to buf at the specified offset as little-endian. The value must be a JavaScript number. Behavior is undefined when value is anything other than a JavaScript number.

      import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(8);

buf.writeDoubleLE(123.456, 0);

console.log(buf);
// Prints: <Buffer 77 be 9f 1a 2f dd 5e 40>
      @param value

      Number to be written to buf.

      @param offset

      Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 8.

      @returns

      offset plus the number of bytes written.

    • value: number,
      offset?: number
      ): number;

      Writes value to buf at the specified offset as big-endian. Behavior is undefined when value is anything other than a JavaScript number.

      import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(4);

buf.writeFloatBE(0xcafebabe, 0);

console.log(buf);
// Prints: <Buffer 4f 4a fe bb>
      @param value

      Number to be written to buf.

      @param offset

      Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 4.

      @returns

      offset plus the number of bytes written.

    • value: number,
      offset?: number
      ): number;

      Writes value to buf at the specified offset as little-endian. Behavior is undefined when value is anything other than a JavaScript number.

      import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(4);

buf.writeFloatLE(0xcafebabe, 0);

console.log(buf);
// Prints: <Buffer bb fe 4a 4f>
      @param value

      Number to be written to buf.

      @param offset

      Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 4.

      @returns

      offset plus the number of bytes written.

    • value: number,
      offset?: number
      ): number;

      Writes value to buf at the specified offset as big-endian. The value must be a valid signed 16-bit integer. Behavior is undefined when value is anything other than a signed 16-bit integer.

      The value is interpreted and written as a two's complement signed integer.

      import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(2);

buf.writeInt16BE(0x0102, 0);

console.log(buf);
// Prints: <Buffer 01 02>
      @param value

      Number to be written to buf.

      @param offset

      Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 2.

      @returns

      offset plus the number of bytes written.

    • value: number,
      offset?: number
      ): number;

      Writes value to buf at the specified offset as little-endian. The value must be a valid signed 16-bit integer. Behavior is undefined when value is anything other than a signed 16-bit integer.

      The value is interpreted and written as a two's complement signed integer.

      import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(2);

buf.writeInt16LE(0x0304, 0);

console.log(buf);
// Prints: <Buffer 04 03>
      @param value

      Number to be written to buf.

      @param offset

      Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 2.

      @returns

      offset plus the number of bytes written.

    • value: number,
      offset?: number
      ): number;

      Writes value to buf at the specified offset as big-endian. The value must be a valid signed 32-bit integer. Behavior is undefined when value is anything other than a signed 32-bit integer.

      The value is interpreted and written as a two's complement signed integer.

      import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(4);

buf.writeInt32BE(0x01020304, 0);

console.log(buf);
// Prints: <Buffer 01 02 03 04>
      @param value

      Number to be written to buf.

      @param offset

      Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 4.

      @returns

      offset plus the number of bytes written.

    • value: number,
      offset?: number
      ): number;

      Writes value to buf at the specified offset as little-endian. The value must be a valid signed 32-bit integer. Behavior is undefined when value is anything other than a signed 32-bit integer.

      The value is interpreted and written as a two's complement signed integer.

      import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(4);

buf.writeInt32LE(0x05060708, 0);

console.log(buf);
// Prints: <Buffer 08 07 06 05>
      @param value

      Number to be written to buf.

      @param offset

      Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 4.

      @returns

      offset plus the number of bytes written.

    • value: number,
      offset?: number
      ): number;

      Writes value to buf at the specified offset. value must be a valid signed 8-bit integer. Behavior is undefined when value is anything other than a signed 8-bit integer.

      value is interpreted and written as a two's complement signed integer.

      import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(2);

buf.writeInt8(2, 0);
buf.writeInt8(-2, 1);

console.log(buf);
// Prints: <Buffer 02 fe>
      @param value

      Number to be written to buf.

      @param offset

      Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 1.

      @returns

      offset plus the number of bytes written.

    • value: number,
      offset: number,
      byteLength: number
      ): number;

      Writes byteLength bytes of value to buf at the specified offsetas big-endian. Supports up to 48 bits of accuracy. Behavior is undefined whenvalue is anything other than a signed integer.

      import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(6);

buf.writeIntBE(0x1234567890ab, 0, 6);

console.log(buf);
// Prints: <Buffer 12 34 56 78 90 ab>
      @param value

      Number to be written to buf.

      @param offset

      Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - byteLength.

      @param byteLength

      Number of bytes to write. Must satisfy 0 < byteLength <= 6.

      @returns

      offset plus the number of bytes written.

    • value: number,
      offset: number,
      byteLength: number
      ): number;

      Writes byteLength bytes of value to buf at the specified offsetas little-endian. Supports up to 48 bits of accuracy. Behavior is undefined when value is anything other than a signed integer.

      import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(6);

buf.writeIntLE(0x1234567890ab, 0, 6);

console.log(buf);
// Prints: <Buffer ab 90 78 56 34 12>
      @param value

      Number to be written to buf.

      @param offset

      Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - byteLength.

      @param byteLength

      Number of bytes to write. Must satisfy 0 < byteLength <= 6.

      @returns

      offset plus the number of bytes written.

    • value: number,
      offset?: number
      ): number;
    • value: number,
      offset?: number
      ): number;

      Writes value to buf at the specified offset as big-endian. The value must be a valid unsigned 16-bit integer. Behavior is undefined when valueis anything other than an unsigned 16-bit integer.

      This function is also available under the writeUint16BE alias.

      import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(4);

buf.writeUInt16BE(0xdead, 0);
buf.writeUInt16BE(0xbeef, 2);

console.log(buf);
// Prints: <Buffer de ad be ef>
      @param value

      Number to be written to buf.

      @param offset

      Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 2.

      @returns

      offset plus the number of bytes written.

    • value: number,
      offset?: number
      ): number;
    • value: number,
      offset?: number
      ): number;

      Writes value to buf at the specified offset as little-endian. The value must be a valid unsigned 16-bit integer. Behavior is undefined when value is anything other than an unsigned 16-bit integer.

      This function is also available under the writeUint16LE alias.

      import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(4);

buf.writeUInt16LE(0xdead, 0);
buf.writeUInt16LE(0xbeef, 2);

console.log(buf);
// Prints: <Buffer ad de ef be>
      @param value

      Number to be written to buf.

      @param offset

      Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 2.

      @returns

      offset plus the number of bytes written.

    • value: number,
      offset?: number
      ): number;
    • value: number,
      offset?: number
      ): number;

      Writes value to buf at the specified offset as big-endian. The value must be a valid unsigned 32-bit integer. Behavior is undefined when valueis anything other than an unsigned 32-bit integer.

      This function is also available under the writeUint32BE alias.

      import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(4);

buf.writeUInt32BE(0xfeedface, 0);

console.log(buf);
// Prints: <Buffer fe ed fa ce>
      @param value

      Number to be written to buf.

      @param offset

      Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 4.

      @returns

      offset plus the number of bytes written.

    • value: number,
      offset?: number
      ): number;
    • value: number,
      offset?: number
      ): number;

      Writes value to buf at the specified offset as little-endian. The value must be a valid unsigned 32-bit integer. Behavior is undefined when value is anything other than an unsigned 32-bit integer.

      This function is also available under the writeUint32LE alias.

      import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(4);

buf.writeUInt32LE(0xfeedface, 0);

console.log(buf);
// Prints: <Buffer ce fa ed fe>
      @param value

      Number to be written to buf.

      @param offset

      Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 4.

      @returns

      offset plus the number of bytes written.

    • value: number,
      offset?: number
      ): number;
    • value: number,
      offset?: number
      ): number;

      Writes value to buf at the specified offset. value must be a valid unsigned 8-bit integer. Behavior is undefined when value is anything other than an unsigned 8-bit integer.

      This function is also available under the writeUint8 alias.

      import { Buffer } from 'node:buffer';

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>
      @param value

      Number to be written to buf.

      @param offset

      Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 1.

      @returns

      offset plus the number of bytes written.

    • value: number,
      offset: number,
      byteLength: number
      ): number;
    • value: number,
      offset: number,
      byteLength: number
      ): number;

      Writes byteLength bytes of value to buf at the specified offsetas big-endian. Supports up to 48 bits of accuracy. Behavior is undefined when value is anything other than an unsigned integer.

      This function is also available under the writeUintBE alias.

      import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(6);

buf.writeUIntBE(0x1234567890ab, 0, 6);

console.log(buf);
// Prints: <Buffer 12 34 56 78 90 ab>
      @param value

      Number to be written to buf.

      @param offset

      Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - byteLength.

      @param byteLength

      Number of bytes to write. Must satisfy 0 < byteLength <= 6.

      @returns

      offset plus the number of bytes written.

    • value: number,
      offset: number,
      byteLength: number
      ): number;
    • value: number,
      offset: number,
      byteLength: number
      ): number;

      Writes byteLength bytes of value to buf at the specified offsetas little-endian. Supports up to 48 bits of accuracy. Behavior is undefined when value is anything other than an unsigned integer.

      This function is also available under the writeUintLE alias.

      import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(6);

buf.writeUIntLE(0x1234567890ab, 0, 6);

console.log(buf);
// Prints: <Buffer ab 90 78 56 34 12>
      @param value

      Number to be written to buf.

      @param offset

      Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - byteLength.

      @param byteLength

      Number of bytes to write. Must satisfy 0 < byteLength <= 6.

      @returns

      offset plus the number of bytes written.

  • interface FileOptions

    • endings?: 'transparent' | 'native'

      One of either 'transparent' or 'native'. When set to 'native', line endings in string source parts will be converted to the platform native line-ending as specified by import { EOL } from 'node:os'.

    • lastModified?: number

      The last modified date of the file. Default: Date.now().

    • type?: string

      The File content-type.

  • type AllowSharedBuffer = Buffer<ArrayBufferLike>
  • type ImplicitArrayBuffer<T extends WithImplicitCoercion<ArrayBufferLike>> = T extends { valueOf(): V } ? V : T
  • type TranscodeEncoding = 'ascii' | 'utf8' | 'utf-8' | 'utf16le' | 'utf-16le' | 'ucs2' | 'ucs-2' | 'latin1' | 'binary'
  • type WithImplicitCoercion<T> = T | { valueOf(): T } | T extends string ? { [toPrimitive](hint: 'string'): T<T> } : never