Calculate SHA-256 hash (browser)

OSCC · JavaScript, Browser, Promise · Oct 13, 2021

Creates a hash for a value using the SHA-256 algorithm. Returns a promise.

  • Use the SubtleCrypto API to create a hash for the given value.
  • Create a new TextEncoder and use it to encode val. Pass its value to SubtleCrypto.digest() to generate a digest of the given data.
  • Use DataView.prototype.getUint32() to read data from the resolved ArrayBuffer.
  • Convert the data to its hexadecimal representation using Number.prototype.toString(). Add the data to an array using Array.prototype.push().
  • Finally, use Array.prototype.join() to combine values in the array of hexes into a string.
const hashBrowser = val =>
    .digest('SHA-256', new TextEncoder('utf-8').encode(val))
    .then(h => {
      let hexes = [],
        view = new DataView(h);
      for (let i = 0; i < view.byteLength; i += 4)
        hexes.push(('00000000' + view.getUint32(i).toString(16)).slice(-8));
      return hexes.join('');
  JSON.stringify({ a: 'a', b: [1, 2, 3, 4], foo: { c: 'bar' } })
// '04aa106279f5977f59f9067fa9712afc4aedc6f5862a8defc34552d8c7206393'

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