hash.js

/*
 * Simple hash function that uses Web Cryptography API
 * @param {string} algo - SHA-1/SHA-256/SHA-384/SHA-512
 * @param {string} text - text to compute digest from
 * @return {Promise} - A promise returning text. 
 */
function hash (algo, text) {
  const encoded = new TextEncoder().encode(text);
  return window.crypto.subtle.digest(algo, encoded)
    .then(result =>
      Array.from(new Uint8Array(result)) // => [ 123, 80, 44, 58, ... ]
        .map(char => char.toString(16))  // => [ '7b', '50', '2c', '3a', ... ]
        .join('')                        // => '7b502c3a...'
    );
}

// Example
hash('SHA-1', 'Hello world').then(console.log)
// Prints out 7b502c3a1f48c8609ae212cdfb639dee39673f5e