interface Buffer
extends Uint8Array
Usage in Deno
```typescript import { type Buffer } from "node:node__buffer.d.ts"; ```
write(string: string,encoding?: BufferEncoding,): number
Writes `string` to `buf` at `offset` according to the character encoding in`encoding`. 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.
```js
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
```
write(): number
write(): number
toString(): string
Decodes `buf` to a string according to the specified character encoding in`encoding`. `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](../.././node__buffer.d.ts/~/constants.MAX_STRING_LENGTH).
```js
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
```
toJSON(): { type: "Buffer"; data: number[]; }
Returns a JSON representation of `buf`. [`JSON.stringify()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/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)`.
```js
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:
```
equals(otherBuffer: Uint8Array): boolean
Returns `true` if both `buf` and `otherBuffer` have exactly the same bytes,`false` otherwise. Equivalent to `buf.compare(otherBuffer) === 0`.
```js
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
```
compare(target: Uint8Array,targetStart?: number,targetEnd?: number,sourceStart?: number,sourceEnd?: number,): -1
| 0
| 1
Compares `buf` with `target` and returns a number indicating whether `buf`comes 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 _before_`buf` when sorted.
* `-1` is returned if `target` should come _after_`buf` when sorted.
```js
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: [ , , ]
// (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.
```js
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`.
copy(target: Uint8Array,targetStart?: number,sourceStart?: number,sourceEnd?: number,): number
Copies data from a region of `buf` to a region in `target`, even if the `target`memory region overlaps with `buf`.
[`TypedArray.prototype.set()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray/set) performs the same operation, and is available
for all TypedArrays, including Node.js `Buffer`s, although it takes
different function arguments.
```js
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!!!!!!!!!!!!!
```
```js
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
```
deprecated
slice(start?: number,end?: number,): Buffer & WithArrayBufferLike<ArrayBuffer>
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, use`Uint8Array.prototype.slice()`.
```js
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 (!)
```
subarray(start?: number,end?: number,): Buffer & WithArrayBufferLike<this["buffer"]>
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()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray/subarray).
Modifying the new `Buffer` slice will modify the memory in the original `Buffer`because the allocated memory of the two objects overlap.
```js
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.
```js
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).)
```
writeBigInt64BE(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.
```js
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(8);
buf.writeBigInt64BE(0x0102030405060708n, 0);
console.log(buf);
// Prints:
```
writeBigInt64LE(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.
```js
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(8);
buf.writeBigInt64LE(0x0102030405060708n, 0);
console.log(buf);
// Prints:
```
writeBigUInt64BE(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.
```js
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(8);
buf.writeBigUInt64BE(0xdecafafecacefaden, 0);
console.log(buf);
// Prints:
```
writeBigUint64BE(value: bigint,offset?: number,): number
writeBigUInt64LE(value: bigint,offset?: number,): number
Writes `value` to `buf` at the specified `offset` as little-endian
```js
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(8);
buf.writeBigUInt64LE(0xdecafafecacefaden, 0);
console.log(buf);
// Prints:
```
This function is also available under the `writeBigUint64LE` alias.
writeBigUint64LE(value: bigint,offset?: number,): number
writeUIntLE(value: number,offset: number,byteLength: number,): number
Writes `byteLength` bytes of `value` to `buf` at the specified `offset`as 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.
```js
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(6);
buf.writeUIntLE(0x1234567890ab, 0, 6);
console.log(buf);
// Prints:
```
writeUintLE(value: number,offset: number,byteLength: number,): number
writeUIntBE(value: number,offset: number,byteLength: number,): number
Writes `byteLength` bytes of `value` to `buf` at the specified `offset`as 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.
```js
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(6);
buf.writeUIntBE(0x1234567890ab, 0, 6);
console.log(buf);
// Prints:
```
writeUintBE(value: number,offset: number,byteLength: number,): number
writeIntLE(value: number,offset: number,byteLength: number,): number
Writes `byteLength` bytes of `value` to `buf` at the specified `offset`as little-endian. Supports up to 48 bits of accuracy. Behavior is undefined
when `value` is anything other than a signed integer.
```js
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(6);
buf.writeIntLE(0x1234567890ab, 0, 6);
console.log(buf);
// Prints:
```
writeIntBE(value: number,offset: number,byteLength: number,): number
Writes `byteLength` bytes of `value` to `buf` at the specified `offset`as big-endian. Supports up to 48 bits of accuracy. Behavior is undefined when`value` is anything other than a
signed integer.
```js
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(6);
buf.writeIntBE(0x1234567890ab, 0, 6);
console.log(buf);
// Prints:
```
readBigUInt64BE(offset?: number): bigint
Reads an unsigned, big-endian 64-bit integer from `buf` at the specified`offset`.
This function is also available under the `readBigUint64BE` alias.
```js
import { Buffer } from 'node:buffer';
const buf = Buffer.from([0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff]);
console.log(buf.readBigUInt64BE(0));
// Prints: 4294967295n
```
readBigUint64BE(offset?: number): bigint
readBigUInt64LE(offset?: number): bigint
Reads an unsigned, little-endian 64-bit integer from `buf` at the specified`offset`.
This function is also available under the `readBigUint64LE` alias.
```js
import { Buffer } from 'node:buffer';
const buf = Buffer.from([0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff]);
console.log(buf.readBigUInt64LE(0));
// Prints: 18446744069414584320n
```
readBigUint64LE(offset?: number): bigint
readBigInt64BE(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.
readBigInt64LE(offset?: number): bigint
Reads a signed, little-endian 64-bit integer from `buf` at the specified`offset`.
Integers read from a `Buffer` are interpreted as two's complement signed
values.
readUIntLE(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.
```js
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
```
readUintLE(offset: number,byteLength: number,): number
readUIntBE(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.
```js
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.
```
readUintBE(offset: number,byteLength: number,): number
readIntLE(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.
```js
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
```
readIntBE(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.
```js
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.
```
readUInt8(offset?: number): number
Reads an unsigned 8-bit integer from `buf` at the specified `offset`.
This function is also available under the `readUint8` alias.
```js
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.
```
readUint8(offset?: number): number
readUInt16LE(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.
```js
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.
```
readUint16LE(offset?: number): number
readUInt16BE(offset?: number): number
Reads an unsigned, big-endian 16-bit integer from `buf` at the specified`offset`.
This function is also available under the `readUint16BE` alias.
```js
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
```
readUint16BE(offset?: number): number
readUInt32LE(offset?: number): number
Reads an unsigned, little-endian 32-bit integer from `buf` at the specified`offset`.
This function is also available under the `readUint32LE` alias.
```js
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.
```
readUint32LE(offset?: number): number
readUInt32BE(offset?: number): number
Reads an unsigned, big-endian 32-bit integer from `buf` at the specified`offset`.
This function is also available under the `readUint32BE` alias.
```js
import { Buffer } from 'node:buffer';
const buf = Buffer.from([0x12, 0x34, 0x56, 0x78]);
console.log(buf.readUInt32BE(0).toString(16));
// Prints: 12345678
```
readUint32BE(offset?: number): number
readInt8(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.
```js
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.
```
readInt16LE(offset?: number): number
Reads a signed, little-endian 16-bit integer from `buf` at the specified`offset`.
Integers read from a `Buffer` are interpreted as two's complement signed values.
```js
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.
```
readInt16BE(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.
```js
import { Buffer } from 'node:buffer';
const buf = Buffer.from([0, 5]);
console.log(buf.readInt16BE(0));
// Prints: 5
```
readInt32LE(offset?: number): number
Reads a signed, little-endian 32-bit integer from `buf` at the specified`offset`.
Integers read from a `Buffer` are interpreted as two's complement signed values.
```js
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.
```
readInt32BE(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.
```js
import { Buffer } from 'node:buffer';
const buf = Buffer.from([0, 0, 0, 5]);
console.log(buf.readInt32BE(0));
// Prints: 5
```
readFloatLE(offset?: number): number
Reads a 32-bit, little-endian float from `buf` at the specified `offset`.
```js
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.
```
readFloatBE(offset?: number): number
Reads a 32-bit, big-endian float from `buf` at the specified `offset`.
```js
import { Buffer } from 'node:buffer';
const buf = Buffer.from([1, 2, 3, 4]);
console.log(buf.readFloatBE(0));
// Prints: 2.387939260590663e-38
```
readDoubleLE(offset?: number): number
Reads a 64-bit, little-endian double from `buf` at the specified `offset`.
```js
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.
```
readDoubleBE(offset?: number): number
Reads a 64-bit, big-endian double from `buf` at the specified `offset`.
```js
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
```
reverse(): this
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.
```js
import { Buffer } from 'node:buffer';
const buf1 = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]);
console.log(buf1);
// Prints:
buf1.swap16();
console.log(buf1);
// Prints:
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:
```js
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.
```
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.
```js
import { Buffer } from 'node:buffer';
const buf1 = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]);
console.log(buf1);
// Prints:
buf1.swap32();
console.log(buf1);
// Prints:
const buf2 = Buffer.from([0x1, 0x2, 0x3]);
buf2.swap32();
// Throws ERR_INVALID_BUFFER_SIZE.
```
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.
```js
import { Buffer } from 'node:buffer';
const buf1 = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]);
console.log(buf1);
// Prints:
buf1.swap64();
console.log(buf1);
// Prints:
const buf2 = Buffer.from([0x1, 0x2, 0x3]);
buf2.swap64();
// Throws ERR_INVALID_BUFFER_SIZE.
```
writeUInt8(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.
```js
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:
```
writeUint8(value: number,offset?: number,): number
writeUInt16LE(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.
```js
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(4);
buf.writeUInt16LE(0xdead, 0);
buf.writeUInt16LE(0xbeef, 2);
console.log(buf);
// Prints:
```
writeUint16LE(value: number,offset?: number,): number
writeUInt16BE(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 `value`is anything other than an
unsigned 16-bit integer.
This function is also available under the `writeUint16BE` alias.
```js
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(4);
buf.writeUInt16BE(0xdead, 0);
buf.writeUInt16BE(0xbeef, 2);
console.log(buf);
// Prints:
```
writeUint16BE(value: number,offset?: number,): number
writeUInt32LE(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.
```js
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(4);
buf.writeUInt32LE(0xfeedface, 0);
console.log(buf);
// Prints:
```
writeUint32LE(value: number,offset?: number,): number
writeUInt32BE(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 `value`is anything other than an
unsigned 32-bit integer.
This function is also available under the `writeUint32BE` alias.
```js
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(4);
buf.writeUInt32BE(0xfeedface, 0);
console.log(buf);
// Prints:
```
writeUint32BE(value: number,offset?: number,): number
writeInt8(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.
```js
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(2);
buf.writeInt8(2, 0);
buf.writeInt8(-2, 1);
console.log(buf);
// Prints:
```
writeInt16LE(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.
```js
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(2);
buf.writeInt16LE(0x0304, 0);
console.log(buf);
// Prints:
```
writeInt16BE(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.
```js
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(2);
buf.writeInt16BE(0x0102, 0);
console.log(buf);
// Prints:
```
writeInt32LE(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.
```js
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(4);
buf.writeInt32LE(0x05060708, 0);
console.log(buf);
// Prints:
```
writeInt32BE(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.
```js
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(4);
buf.writeInt32BE(0x01020304, 0);
console.log(buf);
// Prints:
```
writeFloatLE(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.
```js
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(4);
buf.writeFloatLE(0xcafebabe, 0);
console.log(buf);
// Prints:
```
writeFloatBE(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.
```js
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(4);
buf.writeFloatBE(0xcafebabe, 0);
console.log(buf);
// Prints:
```
writeDoubleLE(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.
```js
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(8);
buf.writeDoubleLE(123.456, 0);
console.log(buf);
// Prints:
```
writeDoubleBE(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.
```js
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(8);
buf.writeDoubleBE(123.456, 0);
console.log(buf);
// Prints:
```
fill(): this
Fills `buf` with the specified `value`. If the `offset` and `end` are not given,
the entire `buf` will be filled:
```js
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:
```
`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:
```js
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:
```
If `value` contains invalid characters, it is truncated; if no valid
fill data remains, an exception is thrown:
```js
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(5);
console.log(buf.fill('a'));
// Prints:
console.log(buf.fill('aazz', 'hex'));
// Prints:
console.log(buf.fill('zz', 'hex'));
// Throws an exception.
```
indexOf(): number
If `value` is:
* a string, `value` is interpreted according to the character encoding in `encoding`.
* a `Buffer` or [`Uint8Array`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/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`.
```js
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()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/indexOf).
```js
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 and`byteOffset` is at least `buf.length`, `buf.length` will be returned.
lastIndexOf(): number
Identical to `buf.indexOf()`, except the last occurrence of `value` is found
rather than the first occurrence.
```js
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()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/lastIndexOf).
```js
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.
includes(): boolean
Equivalent to `buf.indexOf() !== -1`.
```js
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
```