66 lines
1.7 KiB
Plaintext
66 lines
1.7 KiB
Plaintext
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/**
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* Copyright (c) 2013-present, Facebook, Inc.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*
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* @providesModule shallowEqual
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* @typechecks
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* @flow
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*/
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/*eslint-disable no-self-compare */
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'use strict';
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const hasOwnProperty = Object.prototype.hasOwnProperty;
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/**
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* inlined Object.is polyfill to avoid requiring consumers ship their own
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* https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is
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*/
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function is(x: mixed, y: mixed): boolean {
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// SameValue algorithm
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if (x === y) {
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// Steps 1-5, 7-10
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// Steps 6.b-6.e: +0 != -0
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// Added the nonzero y check to make Flow happy, but it is redundant
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return x !== 0 || y !== 0 || 1 / x === 1 / y;
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} else {
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// Step 6.a: NaN == NaN
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return x !== x && y !== y;
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}
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}
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/**
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* Performs equality by iterating through keys on an object and returning false
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* when any key has values which are not strictly equal between the arguments.
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* Returns true when the values of all keys are strictly equal.
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*/
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function shallowEqual(objA: mixed, objB: mixed): boolean {
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if (is(objA, objB)) {
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return true;
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}
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if (typeof objA !== 'object' || objA === null || typeof objB !== 'object' || objB === null) {
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return false;
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}
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const keysA = Object.keys(objA);
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const keysB = Object.keys(objB);
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if (keysA.length !== keysB.length) {
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return false;
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}
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// Test for A's keys different from B.
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for (let i = 0; i < keysA.length; i++) {
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if (!hasOwnProperty.call(objB, keysA[i]) || !is(objA[keysA[i]], objB[keysA[i]])) {
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return false;
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}
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}
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return true;
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}
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module.exports = shallowEqual;
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