Generate random SHA256 look-alike.

sha256random.js

const hashlen = 256;
const hashbase = 16;

const randomNums = new Uint32Array(hashlen / 32);
window.crypto.getRandomValues(randomNums);

const padNum = (num, base) => {
  const padLen = (32 / Math.sqrt(base));
  const str = num.toString(base);
  return (('0' * padLen) + str).slice(-padLen);
}

const randomSHA256 = randomNums.reduce((agg, val) => (agg + padNum(val, hashbase)), '');