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