react-native/Libraries/Utilities/PolyfillFunctions.js

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/**
* Copyright (c) 2013-present, Facebook, Inc.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*
* @providesModule PolyfillFunctions
* @flow
* @format
*/
'use strict';
const defineLazyObjectProperty = require('defineLazyObjectProperty');
/**
* Sets an object's property. If a property with the same name exists, this will
* replace it but maintain its descriptor configuration. The property will be
* replaced with a lazy getter.
*
* In DEV mode the original property value will be preserved as `original[PropertyName]`
* so that, if necessary, it can be restored. For example, if you want to route
* network requests through DevTools (to trace them):
*
* global.XMLHttpRequest = global.originalXMLHttpRequest;
*
* @see https://github.com/facebook/react-native/issues/934
*/
function polyfillObjectProperty<T>(
object: Object,
name: string,
getValue: () => T,
): void {
const descriptor = Object.getOwnPropertyDescriptor(object, name);
if (__DEV__ && descriptor) {
const backupName = `original${name[0].toUpperCase()}${name.substr(1)}`;
Object.defineProperty(object, backupName, {
...descriptor,
value: object[name],
});
}
const {enumerable, writable, configurable} = descriptor || {};
if (descriptor && !configurable) {
console.error('Failed to set polyfill. ' + name + ' is not configurable.');
return;
}
defineLazyObjectProperty(object, name, {
get: getValue,
enumerable: enumerable !== false,
writable: writable !== false,
});
}
function polyfillGlobal<T>(name: string, getValue: () => T): void {
polyfillObjectProperty(global, name, getValue);
}
module.exports = {polyfillObjectProperty, polyfillGlobal};