在 Javascript 构造函数中引用实例变量 [英] Reference Instance Variables in Javascript Constructor

问题描述

我正在尝试通过执行以下操作来维护对象的状态:

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.
    }; 
};

我想在调用 changeState 方法时将实例变量 foo 设置为bar".

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

例如:

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

据我所知，发生的事情是内部匿名函数中的this"指向窗口.我不确定发生了什么.

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.

我在正确的轨道上吗?有没有更好的方法?

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

推荐答案

除非您在调用函数时指定 this 上下文，否则默认将是全局的(在浏览器中是窗口).

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

替代方案是:-

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

};

或:-

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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