1 /*** 2  * 自定义对象属性迭代器 3  * @type {
     {a: string, b: string}} 4  */ 5 var obj = {a: "JavaScript", b: "Java"}; 6  7 Object.defineProperty(obj, Symbol.iterator, { 8     writable: false, 9     configurable: true,10     enumerable: false,11     value: function () {12         var self = this;13         var index = 0;14         var keys = Object.keys(self);15         return {16             next: function () {17                 return {18                     value: self[keys[index++]],19                     done: index > keys.length20                 }21             }22         }23     }24 });