js復制一個對象用到了那些知識,大神們給我點指示被唄？var cloneObj = function (obj) {      var newObj = {};      if (obj instanceof Array) {          newObj = [];      }      for (var key in obj) {          var val = obj[key];                  newObj[key] = typeof val === 'object' ? cloneObj(val): val;      }      return newObj;  };  //測試    var obj = {a:function(){console.log(this.b.c)},b:{c:1}},  newObj = cloneObj(obj); newObj.b.c=2;obj.a();//1newObj.a();//2