randomFill
This function is similar to {@link randomBytes} but requires the first argument to be a Buffer
that will be filled. It also requires that a callback is passed in.
If the callback
function is not provided, an error will be thrown.
import { Buffer } from 'node:buffer';
const { randomFill } = await import('node:crypto');
const buf = Buffer.alloc(10);
randomFill(buf, (err, buf) => {
if (err) throw err;
console.log(buf.toString('hex'));
});
randomFill(buf, 5, (err, buf) => {
if (err) throw err;
console.log(buf.toString('hex'));
});
// The above is equivalent to the following:
randomFill(buf, 5, 5, (err, buf) => {
if (err) throw err;
console.log(buf.toString('hex'));
});
Any ArrayBuffer
, TypedArray
, or DataView
instance may be passed as buffer
.
While this includes instances of Float32Array
and Float64Array
, this function should not be used to generate random floating-point numbers. The result may contain +Infinity
, -Infinity
, and NaN
, and even if the array contains finite numbers only, they are not drawn from a uniform random distribution and have no meaningful lower or upper bounds.
import { Buffer } from 'node:buffer';
const { randomFill } = await import('node:crypto');
const a = new Uint32Array(10);
randomFill(a, (err, buf) => {
if (err) throw err;
console.log(Buffer.from(buf.buffer, buf.byteOffset, buf.byteLength)
.toString('hex'));
});
const b = new DataView(new ArrayBuffer(10));
randomFill(b, (err, buf) => {
if (err) throw err;
console.log(Buffer.from(buf.buffer, buf.byteOffset, buf.byteLength)
.toString('hex'));
});
const c = new ArrayBuffer(10);
randomFill(c, (err, buf) => {
if (err) throw err;
console.log(Buffer.from(buf).toString('hex'));
});
This API uses libuv's threadpool, which can have surprising and negative performance implications for some applications; see the UV_THREADPOOL_SIZE
documentation for more information.
The asynchronous version of crypto.randomFill()
is carried out in a single threadpool request. To minimize threadpool task length variation, partition large randomFill
requests when doing so as part of fulfilling a client request.
Since
v7.10.0, v6.13.0
Parameters
Must be supplied. The size of the provided buffer
must not be larger than 2**31 - 1
.
size=buffer.length - offset
function(err, buf) {}
.