Question

阅读第4章关于功能的“Javascript:the goods part”时,谈到“The means insign patterns”和“The function insign patterns”(第28页)。

When a function is stored as a property of an object, we call it a method. When a method is invoked, this is bound to that object.

这一点很清楚。随后在同一页:

When a function is not the property of an object, then it is invoked as a function:
var sum = add(3, 4); // sum is 7
When a function is invoked with this pattern, this is bound to the global object. This was a mistake in the design of the language.

我的问题:

1.- With "this is bound to the global object" means that this is bound to the global scope?
2.- With "This was a mistake in the design of the language" means that this should be follow the same rules as the methods follow? ie, bound this to himself?

感谢。 -

www.un.org/Depts/DGACM/index_spanish.htm 所提供的两个答复都很有启发性,而且有充分记录。感谢所有与会者。

Answer 1

1 - Yes

2 如果你读,就在他描述一个在语言设计上错误的例子之后。

var myObject = {
  value: 1
};

myObject.double = function() {
  var that = this;

  var helper = function() {
    alert( in helper, this.value =   + this.value +   and that.value =   + that.value);
    that.value = that.value + that.value;
  }

  helper();
};

myObject.double();
alert( after doubling, myObject.value =   + myObject.value);

警告将表明,在作为物体财产的职能中使用这一规定不会奏效。如果全球物体(如窗户)有一个<代码>,,那么这一提示就会看到这一点。

Answer 2

<代码>window是 Java本的全球物体。如果你确定这样的职能:

function myFunc() {
}

It will be bound to the global object, window and using this inside the function will refer to the window object. If you define a function as a property of an object, such as:

var obj = {
   myMethod: function() {
   }
};

并且使用<条码>,即。

Here is an example: http://jsfiddle.net/williamvanr/qBXF8/

友情链接