String to store in buffer.
Optional encoding: BufferEncodingencoding to use, optional. Default is 'utf8'
Optional since v10.0.0 - Use Buffer.from(string[, encoding]) instead.
Allocates a new buffer of {size} octets.
count of octets to allocate.
since v10.0.0 - Use Buffer.alloc() instead (also see Buffer.allocUnsafe()).
Allocates a new buffer containing the given {array} of octets.
The octets to store.
since v10.0.0 - Use Buffer.from(array) instead.
Produces a Buffer backed by the same allocated memory as the given {ArrayBuffer}/{SharedArrayBuffer}.
The ArrayBuffer with which to share memory.
since v10.0.0 - Use Buffer.from(arrayBuffer[, byteOffset[, length]]) instead.
Allocates a new buffer containing the given {array} of octets.
The octets to store.
since v10.0.0 - Use Buffer.from(array) instead.
Copies the passed {buffer} data onto a new {Buffer} instance.
The buffer to copy.
since v10.0.0 - Use Buffer.from(buffer) instead.
Readonly BYTES_The size in bytes of each element in the array.
Readonly [toReadonly bufferThe ArrayBuffer instance referenced by the array.
Readonly byteThe length in bytes of the array.
Readonly byteThe offset in bytes of the array.
Readonly lengthThe length of the array.
Static poolThis is the size (in bytes) of pre-allocated internal Buffer instances used
for pooling. This value may be modified.
v0.11.3
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 buf1 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.
A Buffer or Uint8Array with which to compare buf.
Optional targetStart: numberThe offset within target at which to begin comparison.
Optional Optional targetEnd: numberThe offset within target at which to end comparison (not inclusive).
Optional Optional sourceStart: numberThe offset within buf at which to begin comparison.
Optional Optional sourceEnd: numberThe offset within buf at which to end comparison (not inclusive).
Optional v0.11.13
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
A Buffer or Uint8Array to copy into.
Optional targetStart: numberThe offset within target at which to begin writing.
Optional Optional sourceStart: numberThe offset within buf from which to begin copying.
Optional Optional sourceEnd: numberThe offset within buf at which to stop copying (not inclusive).
Optional The number of bytes copied.
v0.1.90
Returns the this object after copying a section of the array identified by start and end to the same array starting at position target
If target is negative, it is treated as length+target where length is the length of the array.
If start is negative, it is treated as length+start. If end is negative, it is treated as length+end.
Optional end: numberIf not specified, length of the this object is used as its default value.
Optional 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
A Buffer or Uint8Array with which to compare buf.
v0.11.13
Determines whether all the members of an array satisfy the specified test.
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.
Optional thisArg: anyAn object to which the this keyword can refer in the predicate function. If thisArg is omitted, undefined is used as the this value.
Optional 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
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 & 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.
The value with which to fill buf.
Optional offset: numberNumber of bytes to skip before starting to fill buf.
Optional Optional end: numberWhere to stop filling buf (not inclusive).
Optional Optional encoding: BufferEncodingThe encoding for value if value is a string.
Optional A reference to buf.
v0.5.0
Returns the elements of an array that meet the condition specified in a callback function.
A function that accepts up to three arguments. The filter method calls the predicate function one time for each element in the array.
Optional thisArg: anyAn object to which the this keyword can refer in the predicate function. If thisArg is omitted, undefined is used as the this value.
Optional Returns the value of the first element in the array where predicate is true, and undefined otherwise.
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.
Optional thisArg: anyIf provided, it will be used as the this value for each invocation of predicate. If it is not provided, undefined is used instead.
Optional Returns the index of the first element in the array where predicate is true, and -1 otherwise.
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.
Optional thisArg: anyIf provided, it will be used as the this value for each invocation of predicate. If it is not provided, undefined is used instead.
Optional Returns the value of the last element in the array where predicate is true, and undefined otherwise.
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.
Optional thisArg: anyIf provided, it will be used as the this value for each invocation of predicate. If it is not provided, undefined is used instead.
Optional Optional thisArg: anyOptional Returns the index of the last element in the array where predicate is true, and -1 otherwise.
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.
Optional thisArg: anyIf provided, it will be used as the this value for each invocation of predicate. If it is not provided, undefined is used instead.
Optional Performs the specified action for each element in an array.
A function that accepts up to three arguments. forEach calls the callbackfn function one time for each element in the array.
Optional thisArg: anyAn object to which the this keyword can refer in the callbackfn function. If thisArg is omitted, undefined is used as the this value.
Optional 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
What to search for.
Optional byteOffset: numberWhere to begin searching in buf. If negative, then offset is calculated from the end of buf.
Optional Optional encoding: BufferEncodingIf value is a string, this is its encoding.
Optional true if value was found in buf, false otherwise.
v5.3.0
If value is:
value is interpreted according to the character encoding inencoding.Buffer or Uint8Array, value will be used in its entirety.
To compare a partial Buffer, use buf.subarray.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 aTypeError. 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.
What to search for.
Optional byteOffset: numberWhere to begin searching in buf. If negative, then offset is calculated from the end of buf.
Optional Optional encoding: BufferEncodingIf value is a string, this is the encoding used to determine the binary representation of the string that will be searched for in buf.
Optional The index of the first occurrence of value in buf, or -1 if buf does not contain value.
v1.5.0
Adds all the elements of an array separated by the specified separator string.
Optional separator: stringA 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.
Optional 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 aTypeError. 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.
What to search for.
Optional byteOffset: numberOptional Optional encoding: BufferEncodingIf value is a string, this is the encoding used to determine the binary representation of the string that will be searched for in buf.
Optional The index of the last occurrence of value in buf, or -1 if buf does not contain value.
v6.0.0
Calls a defined callback function on each element of an array, and returns an array that contains the results.
A function that accepts up to three arguments. The map method calls the callbackfn function one time for each element in the array.
Optional thisArg: anyAn object to which the this keyword can refer in the callbackfn function. If thisArg is omitted, undefined is used as the this value.
Optional 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.
Optional offset: numberNumber of bytes to skip before starting to read. Must satisfy: 0 <= offset <= buf.length - 8.
Optional v12.0.0, v10.20.0
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.
Optional offset: numberNumber of bytes to skip before starting to read. Must satisfy: 0 <= offset <= buf.length - 8.
Optional v12.0.0, v10.20.0
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
Optional offset: numberNumber of bytes to skip before starting to read. Must satisfy: 0 <= offset <= buf.length - 8.
Optional v12.0.0, v10.20.0
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
Optional offset: numberNumber of bytes to skip before starting to read. Must satisfy: 0 <= offset <= buf.length - 8.
Optional v12.0.0, v10.20.0
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
Optional offset: numberNumber of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 8.
Optional v0.11.15
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.
Optional offset: numberNumber of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 8.
Optional v0.11.15
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
Optional offset: numberNumber of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 4.
Optional v0.11.15
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.
Optional offset: numberNumber of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 4.
Optional v0.11.15
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
Optional offset: numberNumber of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 2.
Optional v0.5.5
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.
Optional offset: numberNumber of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 2.
Optional v0.5.5
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
Optional offset: numberNumber of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 4.
Optional v0.5.5
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.
Optional offset: numberNumber of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 4.
Optional v0.5.5
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.
Optional offset: numberNumber of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 1.
Optional v0.5.0
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.
Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - byteLength.
Number of bytes to read. Must satisfy 0 < byteLength <= 6.
v0.11.15
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
Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - byteLength.
Number of bytes to read. Must satisfy 0 < byteLength <= 6.
v0.11.15
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
Optional offset: numberNumber of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 2.
Optional v0.5.5
Reads an unsigned, little-endian 16-bit integer from buf at the specifiedoffset.
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.
Optional offset: numberNumber of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 2.
Optional v0.5.5
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
Optional offset: numberNumber of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 4.
Optional v0.5.5
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.
Optional offset: numberNumber of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 4.
Optional v0.5.5
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.
Optional offset: numberNumber of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 1.
Optional v0.5.0
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.
Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - byteLength.
Number of bytes to read. Must satisfy 0 < byteLength <= 6.
v0.11.15
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
Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - byteLength.
Number of bytes to read. Must satisfy 0 < byteLength <= 6.
v0.11.15
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.
A function that accepts up to four arguments. The reduce method calls the callbackfn function one time for each element in the array.
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.
A function that accepts up to four arguments. The reduce method calls the callbackfn function one time for each element in the array.
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.
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.
A function that accepts up to four arguments. The reduceRight method calls the callbackfn function one time for each element in the array.
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.
A function that accepts up to four arguments. The reduceRight method calls the callbackfn function one time for each element in the array.
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.
Returns a new Buffer that references the same memory as the original, but
offset and cropped by the start and end indices.
This method is not compatible with the Uint8Array.prototype.slice(),
which is a superclass of Buffer. To copy the slice, useUint8Array.prototype.slice().
import { Buffer } from 'node:buffer';
const buf = Buffer.from('buffer');
const copiedBuf = Uint8Array.prototype.slice.call(buf);
copiedBuf[0]++;
console.log(copiedBuf.toString());
// Prints: cuffer
console.log(buf.toString());
// Prints: buffer
// With buf.slice(), the original buffer is modified.
const notReallyCopiedBuf = buf.slice();
notReallyCopiedBuf[0]++;
console.log(notReallyCopiedBuf.toString());
// Prints: cuffer
console.log(buf.toString());
// Also prints: cuffer (!)
Optional start: numberWhere the new Buffer will start.
Optional Optional end: numberWhere the new Buffer will end (not inclusive).
Optional v0.3.0
Use subarray instead.
Determines whether the specified callback function returns true for any element of an array.
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.
Optional thisArg: anyAn object to which the this keyword can refer in the predicate function. If thisArg is omitted, undefined is used as the this value.
Optional Sorts an array.
Optional compareFn: ((a, b) => number)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)
Optional
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).)
Optional start: numberWhere the new Buffer will start.
Optional Optional end: numberWhere the new Buffer will end (not inclusive).
Optional v3.0.0
Sets the subtype option and marks the buffer modified.
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.
A reference to buf.
v5.10.0
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.
A reference to buf.
v5.10.0
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.
A reference to buf.
v6.3.0
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 && value.type === 'Buffer' ?
Buffer.from(value) :
value;
});
console.log(copy);
// Prints: <Buffer 01 02 03 04 05>
v0.9.2
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
Optional encoding: BufferEncodingThe character encoding to use.
Optional Optional start: numberThe byte offset to start decoding at.
Optional Optional end: numberThe byte offset to stop decoding at (not inclusive).
Optional v0.1.90
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
String to write to buf.
Optional encoding: BufferEncodingThe character encoding of string.
Optional Number of bytes written.
v0.1.90
Optional encoding: BufferEncodingOptional Optional encoding: BufferEncodingOptional 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>
Number to be written to buf.
Optional offset: numberNumber of bytes to skip before starting to write. Must satisfy: 0 <= offset <= buf.length - 8.
Optional offset plus the number of bytes written.
v12.0.0, v10.20.0
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>
Number to be written to buf.
Optional offset: numberNumber of bytes to skip before starting to write. Must satisfy: 0 <= offset <= buf.length - 8.
Optional offset plus the number of bytes written.
v12.0.0, v10.20.0
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>
Number to be written to buf.
Optional offset: numberNumber of bytes to skip before starting to write. Must satisfy: 0 <= offset <= buf.length - 8.
Optional offset plus the number of bytes written.
v12.0.0, v10.20.0
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.
Number to be written to buf.
Optional offset: numberNumber of bytes to skip before starting to write. Must satisfy: 0 <= offset <= buf.length - 8.
Optional offset plus the number of bytes written.
v12.0.0, v10.20.0
Writes value to buf at the specified offset as big-endian. The valuemust 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>
Number to be written to buf.
Optional offset: numberNumber of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 8.
Optional offset plus the number of bytes written.
v0.11.15
Writes value to buf at the specified offset as little-endian. The valuemust 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>
Number to be written to buf.
Optional offset: numberNumber of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 8.
Optional offset plus the number of bytes written.
v0.11.15
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>
Number to be written to buf.
Optional offset: numberNumber of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 4.
Optional offset plus the number of bytes written.
v0.11.15
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>
Number to be written to buf.
Optional offset: numberNumber of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 4.
Optional offset plus the number of bytes written.
v0.11.15
Writes value to buf at the specified offset as big-endian. The valuemust 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>
Number to be written to buf.
Optional offset: numberNumber of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 2.
Optional offset plus the number of bytes written.
v0.5.5
Writes value to buf at the specified offset as little-endian. The valuemust 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>
Number to be written to buf.
Optional offset: numberNumber of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 2.
Optional offset plus the number of bytes written.
v0.5.5
Writes value to buf at the specified offset as big-endian. The valuemust 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>
Number to be written to buf.
Optional offset: numberNumber of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 4.
Optional offset plus the number of bytes written.
v0.5.5
Writes value to buf at the specified offset as little-endian. The valuemust 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>
Number to be written to buf.
Optional offset: numberNumber of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 4.
Optional offset plus the number of bytes written.
v0.5.5
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>
Number to be written to buf.
Optional offset: numberNumber of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 1.
Optional offset plus the number of bytes written.
v0.5.0
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>
Number to be written to buf.
Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - byteLength.
Number of bytes to write. Must satisfy 0 < byteLength <= 6.
offset plus the number of bytes written.
v0.11.15
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>
Number to be written to buf.
Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - byteLength.
Number of bytes to write. Must satisfy 0 < byteLength <= 6.
offset plus the number of bytes written.
v0.11.15
Writes value to buf at the specified offset as big-endian. The valuemust 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>
Number to be written to buf.
Optional offset: numberNumber of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 2.
Optional offset plus the number of bytes written.
v0.5.5
Writes value to buf at the specified offset as little-endian. The valuemust 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>
Number to be written to buf.
Optional offset: numberNumber of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 2.
Optional offset plus the number of bytes written.
v0.5.5
Writes value to buf at the specified offset as big-endian. The valuemust 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>
Number to be written to buf.
Optional offset: numberNumber of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 4.
Optional offset plus the number of bytes written.
v0.5.5
Writes value to buf at the specified offset as little-endian. The valuemust 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>
Number to be written to buf.
Optional offset: numberNumber of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 4.
Optional offset plus the number of bytes written.
v0.5.5
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>
Number to be written to buf.
Optional offset: numberNumber of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 1.
Optional offset plus the number of bytes written.
v0.5.0
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>
Number to be written to buf.
Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - byteLength.
Number of bytes to write. Must satisfy 0 < byteLength <= 6.
offset plus the number of bytes written.
v0.5.5
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>
Number to be written to buf.
Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - byteLength.
Number of bytes to write. Must satisfy 0 < byteLength <= 6.
offset plus the number of bytes written.
v0.5.5
Static allocAllocates a new Buffer of size bytes. If fill is undefined, theBuffer will be zero-filled.
import { Buffer } from 'node:buffer';
const buf = Buffer.alloc(5);
console.log(buf);
// Prints: <Buffer 00 00 00 00 00>
If size is larger than constants.MAX_LENGTH or smaller than 0, ERR_INVALID_ARG_VALUE is thrown.
If fill is specified, the allocated Buffer will be initialized by calling buf.fill(fill).
import { Buffer } from 'node:buffer';
const buf = Buffer.alloc(5, 'a');
console.log(buf);
// Prints: <Buffer 61 61 61 61 61>
If both fill and encoding are specified, the allocated Buffer will be
initialized by calling buf.fill(fill, encoding).
import { Buffer } from 'node:buffer';
const buf = Buffer.alloc(11, 'aGVsbG8gd29ybGQ=', 'base64');
console.log(buf);
// Prints: <Buffer 68 65 6c 6c 6f 20 77 6f 72 6c 64>
Calling Buffer.alloc() can be measurably slower than the alternative Buffer.allocUnsafe() but ensures that the newly created Buffer instance
contents will never contain sensitive data from previous allocations, including
data that might not have been allocated for Buffers.
A TypeError will be thrown if size is not a number.
The desired length of the new Buffer.
Optional fill: string | number | Uint8ArrayA value to pre-fill the new Buffer with.
Optional Optional encoding: BufferEncodingIf fill is a string, this is its encoding.
Optional v5.10.0
Static allocAllocates a new Buffer of size bytes. If size is larger than constants.MAX_LENGTH or smaller than 0, ERR_INVALID_ARG_VALUE is thrown.
The underlying memory for Buffer instances created in this way is not
initialized. The contents of the newly created Buffer are unknown and may contain sensitive data. Use Buffer.alloc() instead to initializeBuffer instances with zeroes.
import { Buffer } from 'node:buffer';
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>
A TypeError will be thrown if size is not a number.
The Buffer module pre-allocates an internal Buffer instance of
size Buffer.poolSize that is used as a pool for the fast allocation of new Buffer instances created using Buffer.allocUnsafe(), Buffer.from(array), Buffer.concat(), and the
deprecated new Buffer(size) constructor only when size is less than or equal
to Buffer.poolSize >> 1 (floor of Buffer.poolSize divided by two).
Use of this pre-allocated internal memory pool is a key difference between
calling Buffer.alloc(size, fill) vs. Buffer.allocUnsafe(size).fill(fill).
Specifically, Buffer.alloc(size, fill) will never use the internal Bufferpool, while Buffer.allocUnsafe(size).fill(fill)will use the internalBuffer pool if size is less
than or equal to half Buffer.poolSize. The
difference is subtle but can be important when an application requires the
additional performance that Buffer.allocUnsafe() provides.
The desired length of the new Buffer.
v5.10.0
Static allocAllocates a new Buffer of size bytes. If size is larger than constants.MAX_LENGTH or smaller than 0, ERR_INVALID_ARG_VALUE is thrown. A zero-length Buffer is created if
size is 0.
The underlying memory for Buffer instances created in this way is not
initialized. The contents of the newly created Buffer are unknown and may contain sensitive data. Use buf.fill(0) to initialize
such Buffer instances with zeroes.
When using Buffer.allocUnsafe() to allocate new Buffer instances,
allocations under 4 KiB are sliced from a single pre-allocated Buffer. This
allows applications to avoid the garbage collection overhead of creating many
individually allocated Buffer instances. This approach improves both
performance and memory usage by eliminating the need to track and clean up as
many individual ArrayBuffer objects.
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 Buffer instance using Buffer.allocUnsafeSlow() and
then copying out the relevant bits.
import { Buffer } from 'node:buffer';
// 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);
}
});
A TypeError will be thrown if size is not a number.
The desired length of the new Buffer.
v5.12.0
Static byteReturns the byte length of a string when encoded using encoding.
This is not the same as String.prototype.length, which does not account
for the encoding that is used to convert the string into bytes.
For 'base64', 'base64url', and 'hex', 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 Buffer created from the
string.
import { Buffer } from 'node:buffer';
const str = '\u00bd + \u00bc = \u00be';
console.log(`${str}: ${str.length} characters, ` +
`${Buffer.byteLength(str, 'utf8')} bytes`);
// Prints: ½ + ¼ = ¾: 9 characters, 12 bytes
When string is a
Buffer/DataView/[TypedArray](https://developer.mozilla.org/en-US/docs/Web/JavaScript/-
Reference/Global_Objects/TypedArray)/ArrayBuffer/[SharedArrayBuffer](https://develop-
er.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer), the byte length as reported by .byteLengthis returned.
A value to calculate the length of.
Optional encoding: BufferEncodingIf string is a string, this is its encoding.
Optional The number of bytes contained within string.
v0.1.90
Static compareCompares buf1 to buf2, typically for the purpose of sorting arrays ofBuffer instances. This is equivalent to calling buf1.compare(buf2).
import { Buffer } from 'node:buffer';
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].)
Either -1, 0, or 1, depending on the result of the comparison. See compare for details.
v0.11.13
Static concatReturns a new Buffer which is the result of concatenating all the Buffer instances in the list together.
If the list has no items, or if the totalLength is 0, then a new zero-length Buffer is returned.
If totalLength is not provided, it is calculated from the Buffer instances
in list by adding their lengths.
If totalLength is provided, it is coerced to an unsigned integer. If the
combined length of the Buffers in list exceeds totalLength, the result is
truncated to totalLength.
import { Buffer } from 'node:buffer';
// 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
Buffer.concat() may also use the internal Buffer pool like Buffer.allocUnsafe() does.
List of Buffer or Uint8Array instances to concatenate.
Optional totalLength: numberTotal length of the Buffer instances in list when concatenated.
Optional v0.7.11
Static fromAllocates a new Buffer using an array of bytes in the range 0 – 255.
Array entries outside that range will be truncated to fit into it.
import { Buffer } from 'node:buffer';
// Creates a new Buffer containing the UTF-8 bytes of the string 'buffer'.
const buf = Buffer.from([0x62, 0x75, 0x66, 0x66, 0x65, 0x72]);
A TypeError will be thrown if array is not an Array or another type
appropriate for Buffer.from() variants.
Buffer.from(array) and Buffer.from(string) may also use the internalBuffer pool like Buffer.allocUnsafe() does.
Optional byteOffset: numberOptional Optional length: numberOptional v5.10.0
Creates a new Buffer using the passed {data}
data to create a new Buffer
Creates a new Buffer containing the given JavaScript string {str}. If provided, the {encoding} parameter identifies the character encoding. If not provided, {encoding} defaults to 'utf8'.
Optional encoding: BufferEncodingOptional Static isReturns true if obj is a Buffer, false otherwise.
import { Buffer } from 'node:buffer';
Buffer.isBuffer(Buffer.alloc(10)); // true
Buffer.isBuffer(Buffer.from('foo')); // true
Buffer.isBuffer('a string'); // false
Buffer.isBuffer([]); // false
Buffer.isBuffer(new Uint8Array(1024)); // false
v0.1.101
Static isReturns true if encoding is the name of a supported character encoding,
or false otherwise.
import { Buffer } from 'node:buffer';
console.log(Buffer.isEncoding('utf8'));
// Prints: true
console.log(Buffer.isEncoding('hex'));
// Prints: true
console.log(Buffer.isEncoding('utf/8'));
// Prints: false
console.log(Buffer.isEncoding(''));
// Prints: false
A character encoding name to check.
v0.9.1
Static ofGenerated using TypeDoc
Allocates a new buffer containing the given {str}.