FNV hash function, 32/64

fnv.js

/**
 * FNV hash
 * - 32 bit FNV-1a hash
 * - 64 bit FNV-1a hash
 * @link http://isthe.com/chongo/tech/comp/fnv/
 *
 * Usage:
 *   fnv.hash('Hello World', 32) // 3012568359
 *   fnv.hash('Hello World', 64) // 3599595964
 */
const fnv = (function () {
  const primes = {
    32: 0x811c9dc5,
    64: 0xcbf29ce484222325,
  }
  return {
    hash(input = '', length = 32) {
      input = input.toString()
      if (!Object.keys(primes).map(i => Number(i)).includes(length)) 
        throw Error('Length not supported')

      let hval = primes[length] || 32
      for (let i = 0; i < input.length; ++i) {
        hval ^= input.charCodeAt(i)
        hval += length === 32 ? 
          (hval << 1) + (hval << 4) + (hval << 7) + (hval << 8) + (hval << 24) : 
          (hval << 1) + (hval << 4) + (hval << 5) + (hval << 7) + (hval << 40)
      }
      return hval >>> 0
    }
  }
})()