# Interface BufferConstructor

Raw data is stored in instances of the Buffer class. A Buffer is similar to an array of integers but corresponds to a raw memory allocation outside the V8 heap. A Buffer cannot be resized. Valid string encodings: 'ascii'|'utf8'|'utf16le'|'ucs2'(alias of 'utf16le')|'base64'|'base64url'|'binary'(deprecated)|'hex'

#### Hierarchy

- BufferConstructor

#####
Index

### Constructors

constructor

### Properties

poolSize

### Methods

alloc
allocUnsafe
allocUnsafeSlow
byteLength
compare
concat
copyBytesFrom
from
isBuffer
isEncoding
of

## Constructors

### constructor

- new BufferConstructor(str, encoding?): Buffer

- Allocates a new buffer containing the given {str}.

  #### Parameters

  - ##### str: string

    String to store in buffer.

  - ##### `Optional` encoding: BufferEncoding

    encoding to use, optional. Default is 'utf8'

  #### Returns Buffer

  #### Deprecated

  since v10.0.0 - Use `Buffer.from(string[, encoding])` instead.

- new BufferConstructor(size): Buffer

- Allocates a new buffer of {size} octets.

  #### Parameters

  - ##### size: number

    count of octets to allocate.

  #### Returns Buffer

  #### Deprecated

  since v10.0.0 - Use `Buffer.alloc()` instead (also see `Buffer.allocUnsafe()`).

- new BufferConstructor(array): Buffer

- Allocates a new buffer containing the given {array} of octets.

  #### Parameters

  - ##### array: Uint8Array<ArrayBufferLike>

    The octets to store.

  #### Returns Buffer

  #### Deprecated

  since v10.0.0 - Use `Buffer.from(array)` instead.

- new BufferConstructor(arrayBuffer): Buffer

- Produces a Buffer backed by the same allocated memory as the given {ArrayBuffer}/{SharedArrayBuffer}.

  #### Parameters

  - ##### arrayBuffer: ArrayBuffer | SharedArrayBuffer

    The ArrayBuffer with which to share memory.

  #### Returns Buffer

  #### Deprecated

  since v10.0.0 - Use `Buffer.from(arrayBuffer[, byteOffset[, length]])` instead.

- new BufferConstructor(array): Buffer

- Allocates a new buffer containing the given {array} of octets.

  #### Parameters

  - ##### array: readonly any[]

    The octets to store.

  #### Returns Buffer

  #### Deprecated

  since v10.0.0 - Use `Buffer.from(array)` instead.

- new BufferConstructor(buffer): Buffer

- Copies the passed {buffer} data onto a new {Buffer} instance.

  #### Parameters

  - ##### buffer: Buffer

    The buffer to copy.

  #### Returns Buffer

  #### Deprecated

  since v10.0.0 - Use `Buffer.from(buffer)` instead.

## Properties

### poolSize

poolSize: number

This is the size (in bytes) of pre-allocated internal `Buffer` instances used for pooling. This value may be modified.

#### Since

v0.11.3

## Methods

### alloc

- alloc(size, fill?, encoding?): Buffer

- Allocates a new `Buffer` of `size` bytes. If `fill` is `undefined`, the`Buffer` 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_OUT_OF_RANGE` 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 `Buffer`s.

  A `TypeError` will be thrown if `size` is not a number.

  #### Parameters

  - ##### size: number

    The desired length of the new `Buffer`.

  - ##### `Optional` fill: string | number | Uint8Array<ArrayBufferLike>

    A value to pre-fill the new `Buffer` with.

  - ##### `Optional` encoding: BufferEncoding

    If `fill` is a string, this is its encoding.

  #### Returns Buffer

  #### Since

  v5.10.0

### allocUnsafe

- allocUnsafe(size): Buffer

- Allocates a new `Buffer` of `size` bytes. If `size` is larger than constants.MAX_LENGTH or smaller than 0, `ERR_OUT_OF_RANGE` 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 initialize`Buffer` 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)`, and `Buffer.concat()` only when `size` is less than`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 `Buffer`pool, while `Buffer.allocUnsafe(size).fill(fill)`will use the internal`Buffer` 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.

  #### Parameters

  - ##### size: number

    The desired length of the new `Buffer`.

  #### Returns Buffer

  #### Since

  v5.10.0

### allocUnsafeSlow

- allocUnsafeSlow(size): Buffer

- Allocates a new `Buffer` of `size` bytes. If `size` is larger than constants.MAX_LENGTH or smaller than 0, `ERR_OUT_OF_RANGE` 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.

  #### Parameters

  - ##### size: number

    The desired length of the new `Buffer`.

  #### Returns Buffer

  #### Since

  v5.12.0

### byteLength

- byteLength(string, encoding?): number

- Returns 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 `.byteLength`is returned.

  #### Parameters

  - ##### string: string | ArrayBuffer | SharedArrayBuffer | ArrayBufferView

    A value to calculate the length of.

  - ##### `Optional` encoding: BufferEncoding

    If `string` is a string, this is its encoding.

  #### Returns number

  The number of bytes contained within `string`.

  #### Since

  v0.1.90

### compare

- compare(buf1, buf2): 0 | 1 | -1

- Compares `buf1` to `buf2`, typically for the purpose of sorting arrays of`Buffer` 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].)

  #### Parameters

  - ##### buf1: Uint8Array<ArrayBufferLike>

  - ##### buf2: Uint8Array<ArrayBufferLike>

  #### Returns 0 | 1 | -1

  Either `-1`, `0`, or `1`, depending on the result of the comparison. See `compare` for details.

  #### Since

  v0.11.13

### concat

- concat(list, totalLength?): Buffer

- Returns 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 `Buffer`s 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.

  #### Parameters

  - ##### list: readonly Uint8Array<ArrayBufferLike>[]

    List of `Buffer` or Uint8Array instances to concatenate.

  - ##### `Optional` totalLength: number

    Total length of the `Buffer` instances in `list` when concatenated.

  #### Returns Buffer

  #### Since

  v0.7.11

### copyBytesFrom

- copyBytesFrom(view, offset?, length?): Buffer

- Copies the underlying memory of `view` into a new `Buffer`.

      const u16 = new Uint16Array([0, 0xffff]);
      const buf = Buffer.copyBytesFrom(u16, 1, 1);
      u16[1] = 0;
      console.log(buf.length); // 2
      console.log(buf[0]); // 255
      console.log(buf[1]); // 255

  #### Parameters

  - ##### view: TypedArray

    The {TypedArray} to copy.

  - ##### `Optional` offset: number

    The starting offset within `view`.

  - ##### `Optional` length: number

    The number of elements from `view` to copy.

  #### Returns Buffer

  #### Since

  v19.8.0

### from

- from(arrayBuffer, byteOffset?, length?): Buffer

- Allocates 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]);

  If `array` is an `Array`-like object (that is, one with a `length` property of type `number`), it is treated as if it is an array, unless it is a `Buffer` or a `Uint8Array`. This means all other `TypedArray` variants get treated as an`Array`. To create a `Buffer` from the bytes backing a `TypedArray`, use `Buffer.copyBytesFrom()`.

  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 internal`Buffer` pool like `Buffer.allocUnsafe()` does.

  #### Parameters

  - ##### arrayBuffer: WithImplicitCoercion<ArrayBuffer | SharedArrayBuffer>

  - ##### `Optional` byteOffset: number

  - ##### `Optional` length: number

  #### Returns Buffer

  #### Since

  v5.10.0

- from(data): Buffer

- Creates a new Buffer using the passed {data}

  #### Parameters

  - ##### data: Uint8Array<ArrayBufferLike> | readonly number[]

    data to create a new Buffer

  #### Returns Buffer

- from(data): Buffer

- #### Parameters

  - ##### data: WithImplicitCoercion<string | Uint8Array<ArrayBufferLike> | readonly number[]>

  #### Returns Buffer

- from(str, encoding?): 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'.

  #### Parameters

  - ##### str: WithImplicitCoercion<string> | {
    [toPrimitive](hint) => string;
    }

  - ##### `Optional` encoding: BufferEncoding

  #### Returns Buffer

### isBuffer

- isBuffer(obj): obj is Buffer

- Returns `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

  #### Parameters

  - ##### obj: any

  #### Returns obj is Buffer

  #### Since

  v0.1.101

### isEncoding

- isEncoding(encoding): encoding is BufferEncoding

- Returns `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

  #### Parameters

  - ##### encoding: string

    A character encoding name to check.

  #### Returns encoding is BufferEncoding

  #### Since

  v0.9.1

### of

- of(...items): Buffer

- Creates a new Buffer using the passed {data}

  #### Parameters

  - ##### `Rest` ...items: number[]

  #### Returns Buffer

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