function hash(str) {
  let hash = 5381
  let i = str.length

  while(i) {
    hash = (hash * 33) ^ str.charCodeAt(--i);
  }

  /* JavaScript does bitwise operations (like XOR, above) on 32-bit signed
   * integers. Since we want the results to be always positive, convert the
   * signed int to an unsigned by doing an unsigned bitshift. */
  return hash >>> 0;
}


console.log('hash(hello)=', hash('hello').toString(16))
console.log('hash(hello!)=', hash('hello!').toString(16))

const crypto = require('crypto');

const secret = 'abcdefg';
const hash = crypto.createHmac('sha256', secret)
                   .update('I love cupcakes')
                   .digest('hex')
console.log(hash)