hash-sum/hash-sum.js

'use strict';

function pad (hash, len) {
  while (hash.length < len) {
    hash = '0' + hash;
  }
  return hash;
}

function fold (hash, text) {
  var i;
  var chr;
  var len;
  if (text.length === 0) {
    return hash;
  }
  for (i = 0, len = text.length; i < len; i++) {
    chr = text.charCodeAt(i);
    hash = ((hash << 5) - hash) + chr;
    hash |= 0;
  }
  return hash < 0 ? hash * -2 : hash;
}

function foldObject (hash, o) {
  return Object.keys(o).reduce(foldKey, hash);
  function foldKey (hash, key) {
    return foldValue(hash, o[key], key);
  }
}

function foldValue (input, value, key) {
  var hash = fold(fold(fold(input, key), toString(value)), typeof value);
  if (value === null) {
    return fold(hash, 'null');
  }
  if (value === undefined) {
    return fold(hash, 'undefined');
  }
  if (typeof value === 'object') {
    return foldObject(hash, value);
  }
  return fold(hash, value.toString());
}

function toString (o) {
  return Object.prototype.toString.call(o);
}

function sum (o) {
  return pad(foldValue(0, o, '').toString(16), 8);
}

module.exports = sum;