Simple, small, and fast pseudorandom number generator to deterministically generate large amounts of mock test data.

getPseudoRandomValues.js

/**
 * Simple, small, and fast pseudorandom number generator to deterministically generate large amounts of mock test data.
 * 
 * API is intended to follow [`crypto.getRandomValues()`](https://developer.mozilla.org/en-US/docs/Web/API/Crypto/getRandomValues).
 * 
 * Hash function source:
 * - https://burtleburtle.net/bob/hash/integer.html
 * - https://web.archive.org/web/20090408063205/http://www.cris.com/~Ttwang/tech/inthash.htm
 * @param {ArrayBufferView<ArrayBufferLike>} typedArray An integer-based `TypedArray` with a byte length that is a multiple of 4.
 * All elements in the array will be overwritten with random numbers.
 * @param {Number} seed A number to initiate the pseudorandom hash function.
 * @returns {ArrayBufferView<ArrayBufferLike>} The same array passed as `typedArray` but with its contents replaced with pseudorandom
 * numbers. Note that `typedArray` is modified in-place and no copy is made.
 */
function getPseudoRandomValues(typedArray, seed) {
  function hash(n) {
    n = n ^ (n >> 4);
    n = (n ^ 0xdeadbeef) + (n << 5);
    n = n ^ (n >> 11);
    return n;
  }

  const array = new Uint32Array(typedArray.buffer);
  let h = hash(seed);
  for (let i = 0; i < array.length; i++) {
    h = hash(h);
    array[i] = h;
  }
  return typedArray;
}

// Usage example:
// const arr = new Uint8Array(1024 * 1024 * 1024);
// getPseudoRandomValues(arr, 1)