82 lines
1.9 KiB
JavaScript
82 lines
1.9 KiB
JavaScript
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/*!
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* copy-descriptor <https://github.com/jonschlinkert/copy-descriptor>
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*
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* Copyright (c) 2015, Jon Schlinkert.
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* Licensed under the MIT License.
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*/
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'use strict';
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/**
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* Copy a descriptor from one object to another.
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*
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* ```js
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* function App() {
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* this.cache = {};
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* }
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* App.prototype.set = function(key, val) {
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* this.cache[key] = val;
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* return this;
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* };
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* Object.defineProperty(App.prototype, 'count', {
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* get: function() {
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* return Object.keys(this.cache).length;
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* }
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* });
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*
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* copy(App.prototype, 'count', 'len');
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*
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* // create an instance
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* var app = new App();
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*
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* app.set('a', true);
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* app.set('b', true);
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* app.set('c', true);
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*
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* console.log(app.count);
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* //=> 3
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* console.log(app.len);
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* //=> 3
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* ```
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* @name copy
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* @param {Object} `receiver` The target object
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* @param {Object} `provider` The provider object
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* @param {String} `from` The key to copy on provider.
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* @param {String} `to` Optionally specify a new key name to use.
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* @return {Object}
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* @api public
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*/
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module.exports = function copyDescriptor(receiver, provider, from, to) {
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if (!isObject(provider) && typeof provider !== 'function') {
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to = from;
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from = provider;
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provider = receiver;
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}
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if (!isObject(receiver) && typeof receiver !== 'function') {
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throw new TypeError('expected the first argument to be an object');
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}
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if (!isObject(provider) && typeof provider !== 'function') {
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throw new TypeError('expected provider to be an object');
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}
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if (typeof to !== 'string') {
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to = from;
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}
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if (typeof from !== 'string') {
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throw new TypeError('expected key to be a string');
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}
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if (!(from in provider)) {
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throw new Error('property "' + from + '" does not exist');
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}
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var val = Object.getOwnPropertyDescriptor(provider, from);
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if (val) Object.defineProperty(receiver, to, val);
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};
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function isObject(val) {
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return {}.toString.call(val) === '[object Object]';
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}
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