Crypto: getRandomValues() method

Syntax

getRandomValues(typedArray)

Parameters

typedArray

An integer-based TypedArray, that is one of: Int8Array, Uint8Array, Uint8ClampedArray, Int16Array, Uint16Array, Int32Array, Uint32Array, BigInt64Array, BigUint64Array (but not Float16Array, Float32Array nor Float64Array). All elements in the array will be overwritten with random numbers.

Return value

The same array passed as typedArray but with its contents replaced with the newly generated random numbers. Note that typedArray is modified in-place, and no copy is made.

Exceptions

QuotaExceededError

Thrown if the byteLength of typedArray exceeds 65,536.

Usage notes

Prefer the generateKey() method for key generation, which is guaranteed to be running in a secure context.

There is no minimum degree of entropy mandated by the Web Cryptography specification. User agents are instead urged to provide the best entropy they can when generating random numbers, using a well-defined, efficient pseudorandom number generator built into the user agent itself, but seeded with values taken from an external source of pseudorandom numbers, such as a platform-specific random number function, the Unix /dev/urandom device, or other source of random or pseudorandom data.

Examples

const array = new Uint32Array(10);
self.crypto.getRandomValues(array);

console.log("Your lucky numbers:");
for (const num of array) {
  console.log(num);
}

Specifications

Browser compatibility

See also

• Web Crypto API
• Math.random, a non-cryptographic source of random numbers.