JavaScript构造函数中的参考实例变量 [英] Reference Instance Variables in Javascript Constructor

问题描述

我试图通过做这样的事情来保持对象的状态：

  obj = function b $ b this.foo = undefined; 
 this.changeState = function（）{
（function（）{this.foo =bar}）（）; //这是设计的，但是同样的想法。 
}; 
}; 
  

当我调用changeState方法时，我想将实例变量foo设置为bar p>

例如：

  o = new obj 
 o.changeState（）; 
 alert（o.foo）; //这应该说bar
  

据我所知，这个在内部匿名函数指向窗口。我不知道发生了什么。

我在正确的轨道上吗？有没有更好的方法？

解决方案

除非你在调用函数时指定这个上下文，默认将是全局

  obj = 
 function（）{
 this.foo = undefined; 
 this.changeState = function（）{
（function（）{this.foo =bar}）。 //这是设计的，但是同样的想法。 
}; 
  

};

/ p>

  obj = function（）{
 var self = this; 
 this.foo = undefined; 
 this.changeState = function（）{
（function（）{self.foo =bar}）（）; //这是设计的，但是同样的想法。 
}; 
  

};

I'm trying to maintain state on an object by doing something like this:

obj = function() { 
    this.foo = undefined; 
    this.changeState = function () { 
        (function () { this.foo = "bar" })(); // This is contrived, but same idea.
    }; 
};

I want to set the instance variable foo to "bar" when I call the changeState method.

For instance:

o = new obj();
o.changeState();
alert(o.foo); // This should say "bar"

As far as I can tell, what is happening is that "this" in the inner anonymous function is pointing to window. I'm not sure what's going on.

Am I on the right track? Is there a better approach?

解决方案

Unless you specify a this context when calling a function the default will be the global (which in browsers is window).

Alternatives are:-

obj = function() { 
  this.foo = undefined; 
  this.changeState = function () { 
    (function () { this.foo = "bar" }).call(this); // This is contrived, but same idea.
  }; 

};

or:-

obj = function() {
  var self = this;
  this.foo = undefined; 
  this.changeState = function () { 
    (function () { self.foo = "bar" })(); // This is contrived, but same idea.
  }; 

};

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