跟踪对象是否已更改

Question

// A simple Javascript Object / String
var object = "hello";

// Imagine a button in the DOM, and if it's clicked the object value will change
document.getElementById("button").onclick = function(){
   window.object = "hello world";
}

// Now I would like to track and do something when the object is changed, ex:
object.onreadystatechange = function(){
   alert(object);
}

注意:这听起来很愚蠢,因为我可以onclick在按钮上获得事件的变化,但这不是我想要的,我想严格跟踪对象本身的变化以供任何使用,上面的代码是只是一个例子.

Answer 1

Javascript不允许您在任意对象/变量上设置程序化观察点/事件.

您可以使用封装来隐藏对象内部的各个值,只允许通过具有您想要的副作用的专用"setter"函数来修改它们.

Answer 2

那么你可以使用get和set方法使它成为一个实际的对象:

// A simple Javascript Object 
var object = new (function(){
    this.text = 'hello';

    this.setText = function(msg){
         this.text = msg
         //on change event
    }
})();

// Imagine a button in the DOM, and if it's clicked the object value will change
document.getElementById("button").onclick = function(){
   object.setText('New Text');
}

这是一个演示小提琴:http://jsfiddle.net/maniator/BSYpz/