30-seconds-of-code/snippets/hashBrowser.md

title, tags

title	tags
hashBrowser	browser,promise,advanced

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, passing its value to SubtleCrypto.digest() to generate a digest of the given data.
• Use DataView.prototype.getUint32() to read data from the resolved ArrayBuffer.
• Add the data to an array using Array.prototype.push() after converting it to its hexadecimal representation using Number.prototype.toString(16).
• Finally, use Array.prototype.join() to combine values in the array of hexes into a string.

const hashBrowser = val =>
  crypto.subtle
    .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('');
    });

hashBrowser(
  JSON.stringify({ a: 'a', b: [1, 2, 3, 4], foo: { c: 'bar' } })
).then(console.log);
// '04aa106279f5977f59f9067fa9712afc4aedc6f5862a8defc34552d8c7206393'