Deep Equality from Mongoose

deepEqual_Mongoose.js

exports.deepEqual = function deepEqual (a, b) {
  if (a === b) return true;

  if (a instanceof Date && b instanceof Date)
    return a.getTime() === b.getTime();

  if (a instanceof ObjectId && b instanceof ObjectId) {
    return a.toString() === b.toString();
  }

  if (a instanceof RegExp && b instanceof RegExp) {
    return a.source == b.source &&
           a.ignoreCase == b.ignoreCase &&
           a.multiline == b.multiline &&
           a.global == b.global;
  }

  if (typeof a !== 'object' && typeof b !== 'object')
    return a == b;

  if (a === null || b === null || a === undefined || b === undefined)
    return false

  if (a.prototype !== b.prototype) return false;

  // Handle MongooseNumbers
  if (a instanceof Number && b instanceof Number) {
    return a.valueOf() === b.valueOf();
  }

  if (Buffer.isBuffer(a)) {
    return exports.buffer.areEqual(a, b);
  }

  if (isMongooseObject(a)) a = a.toObject();
  if (isMongooseObject(b)) b = b.toObject();

  try {
    var ka = Object.keys(a),
        kb = Object.keys(b),
        key, i;
  } catch (e) {//happens when one is a string literal and the other isn't
    return false;
  }

  // having the same number of owned properties (keys incorporates
  // hasOwnProperty)
  if (ka.length != kb.length)
    return false;

  //the same set of keys (although not necessarily the same order),
  ka.sort();
  kb.sort();

  //~~~cheap key test
  for (i = ka.length - 1; i >= 0; i--) {
    if (ka[i] != kb[i])
      return false;
  }

  //equivalent values for every corresponding key, and
  //~~~possibly expensive deep test
  for (i = ka.length - 1; i >= 0; i--) {
    key = ka[i];
    if (!deepEqual(a[key], b[key])) return false;
  }

  return true;
};