“这个”闭包中的关键字 [英] "this" keyword inside closure

问题描述

请看下面的代码：

  var test =（function（）{
 var t =test; 
 return {
 alertT：function （）{
 alert（t）; 
} 
} 
}（））; 
  

我在window.load上有一个函数，如：

  test.alertT（）; 
  

这一切都很好。但是，当我尝试在 alert（）中在 alertT 中显式设置 t 的上下文时，

我试过：

  var that = this; 
 alert（that.t）; // undefined 
  

我试过：

  return {
：this，
 alertT：function（）{
 alert（that.t）; // undefined！ 
} 
} 
  

我试过：

  var test =（function（）{
 var t =test; 
 var myObj = this; 
 return {
 alertT：function（）{
 alert（myObj.t）; // undefined！
} 
} 
} 
  

我缺少什么？我需要能够明确地为回调等事情设置上下文。我也看到了例子（http://stackoverflow.com/questions/346015/javascript-closures-and-this-context），看起来像什么

解决方案

t 只是外部匿名函数范围内的正常变量（因此也是内部匿名函数）。它不是一个对象上的属性，所以你只需设置它不需要引用 this ，， code> the_other 。

  var test =（function（）{
 var t =test; 
 return {
 alertT：function（）{
 alert（t）; 
}，
 setT：function（new_value）{
t = new_value; 
} 
} 
}（））; 
 test.alertT（）; 
 test.setT（'hello，world'）; 
 test.alertT（）; 
  

您使用的语法是创建在JS中作为私有变量的东西的通常模式。

I've seen a bunch of examples but can't seem to get some sample code to work.

Take the following code:

var test = (function(){
    var t = "test";
    return {
        alertT: function(){ 
            alert(t);
        }
    }
}());

and I have a function on window.load like:

test.alertT();

That all works fine. However, when I try to explicitly set the context of t inside the alert() in alertT, I just get undefined.

I've tried:

var that = this;
alert(that.t); //undefined

I've tried:

        return {
            that: this,
            alertT: function(){ 
                alert(that.t); // undefined!
            }
        }

and I've tried:

var test = (function(){
    var t = "test";
    var myObj = this;
    return {
        alertT: function(){ 
            alert(myObj.t); // undefined!
        }
    }
}());

what am I missing? I need to be able to set the context explicitly for things like callbacks etc. I've seen examples too (http://stackoverflow.com/questions/346015/javascript-closures-and-this-context) that seem like what I'm doing, so why does this not work?

解决方案

t is just a normal variable in the scope of the outside anonymous function (and thus also the inner anonymous function). It isn't a property on an object, so you simply set it without reference to this, that, or the_other.

var test = (function(){
    var t = "test";
    return {
        alertT: function(){ 
            alert(t);
        },
        setT: function (new_value) {
            t = new_value;
        }
    }
}());
test.alertT();
test.setT('hello, world');
test.alertT();

The syntax you are using is the usual pattern for creating something that acts like a private variable in JS.

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