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1/**
2 * Copyright (c) 2013-present, Facebook, Inc.
3 *
4 * This source code is licensed under the MIT license found in the
5 * LICENSE file in the root directory of this source tree.
6 *
7 * @typechecks
8 *
9 */
10/*eslint-disable no-self-compare */
11'use strict';
12const hasOwnProperty = Object.prototype.hasOwnProperty;
13/**
14 * inlined Object.is polyfill to avoid requiring consumers ship their own
15 * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is
16 */
17const is = (x, y) => {
18 // SameValue algorithm
19 if (x === y) {
20 // Steps 1-5, 7-10
21 // Steps 6.b-6.e: +0 != -0
22 // Added the nonzero y check to make Flow happy, but it is redundant
23 return x !== 0 || y !== 0 || 1 / x === 1 / y;
24 }
25 else {
26 // Step 6.a: NaN == NaN
27 return x !== x && y !== y;
28 }
29};
30/**
31 * Performs equality by iterating through keys on an object and returning false
32 * when any key has values which are not strictly equal between the arguments.
33 * Returns true when the values of all keys are strictly equal.
34 */
35export const shallowEqual = (objA, objB) => {
36 if (is(objA, objB)) {
37 return true;
38 }
39 if (typeof objA !== 'object' || objA === null || typeof objB !== 'object' || objB === null) {
40 return false;
41 }
42 var keysA = Object.keys(objA);
43 var keysB = Object.keys(objB);
44 if (keysA.length !== keysB.length) {
45 return false;
46 }
47 // Test for A's keys different from B.
48 for (var i = 0; i < keysA.length; i++) {
49 if (!hasOwnProperty.call(objB, keysA[i]) || !is(objA[keysA[i]], objB[keysA[i]])) {
50 return false;
51 }
52 }
53 return true;
54};