Interface BufferConstructor

Allocates a new Buffer of size bytes. If fill is undefined, theBuffer will be zero-filled.

import { Buffer } from '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 '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 '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.

Since

v5.10.0

Allocates 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 '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 newBuffer instances created using Buffer.allocUnsafe(),Buffer.from(array), Buffer.concat(), and the deprecatednew 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.

Since

v5.10.0

Allocates 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 KB 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 '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.

Since

v5.12.0

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 '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.

Since

v0.1.90

Returns

The number of bytes contained within string.

Compares buf1 to buf2, typically for the purpose of sorting arrays ofBuffer instances. This is equivalent to calling buf1.compare(buf2).

import { Buffer } from '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].)

Since

v0.11.13

Returns

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

Returns a new Buffer which is the result of concatenating all the Bufferinstances in the list together.

If the list has no items, or if the totalLength is 0, then a new zero-lengthBuffer 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 '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.

Since

v0.7.11

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 '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.

Since

v5.10.0

Creates a new Buffer using the passed {data}

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'.

Returns true if obj is a Buffer, false otherwise.

import { Buffer } from '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

Since

v0.1.101

Returns true if encoding is the name of a supported character encoding, or false otherwise.

import { Buffer } from '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

Since

v0.9.1

Creates a new Buffer using the passed {data}