shallowEqual.js

/**
 * Copyright 2013 Facebook, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * @providesModule shallowEqual
 */

"use strict";

/**
 * Performs equality by iterating through keys on an object and returning
 * false when any key has values which are not strictly equal between
 * objA and objB. Returns true when the values of all keys are strictly equal.
 *
 * @return {boolean}
 */
function shallowEqual(objA, objB) {
  if (objA === objB) {
    return true;
  }
  var key;
  // Test for A's keys different from B.
  for (key in objA) {
    if (objA.hasOwnProperty(key) &&
        (!objB.hasOwnProperty(key) || objA[key] !== objB[key])) {
      return false;
    }
  }
  // Test for B'a keys missing from A.
  for (key in objB) {
    if (objB.hasOwnProperty(key) && !objA.hasOwnProperty(key)) {
      return false;
    }
  }
  return true;
}

module.exports = shallowEqual;