javascript - 监听JavaScript中的变量更改(Listening for variable changes in JavaScript)

Question

Is it possible to have an event in JS that fires when the value of a certain variable changes?(某个变量的值更改时，是否可能在JS中触发事件？)

JQuery is accepted.(接受JQuery。)   ask by rashcroft22 translate from so

Answer 1

Yes, this is now completely possible!(是的，现在完全有可能！)

I know this is an old thread but now this effect is possible using accessors (getters and setters): https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Working_with_Objects#Defining_getters_and_setters(我知道这是一个旧线程，但是现在可以使用访问器（获取器和设置器）实现这种效果： https : //developer.mozilla.org/zh-CN/docs/Web/JavaScript/Guide/Working_with_Objects#Defining_getters_and_setters) You can define an object like this, in which aInternal represents the field a :(您可以定义一个这样的对象，其中aInternal表示字段a ：) x = { aInternal: 10, aListener: function(val) {}, set a(val) { this.aInternal = val; this.aListener(val); }, get a() { return this.aInternal; }, registerListener: function(listener) { this.aListener = listener; } } Then you can register a listener using the following:(然后，您可以使用以下方法注册侦听器：) x.registerListener(function(val) { alert("Someone changed the value of x.a to " + val); }); So whenever anything changes the value of xa , the listener function will be fired.(因此，只要有什么改变xa的值，就会触发监听器函数。) Running the following line will bring the alert popup:(运行以下行将弹出警报弹出窗口：) x.a = 42; See an example here: https://jsfiddle.net/5o1wf1bn/1/(在此处查看示例： https ： //jsfiddle.net/5o1wf1bn/1/) You can also user an array of listeners instead of a single listener slot, but I wanted to give you the simplest possible example.(您还可以使用一组侦听器而不是一个侦听器插槽，但是我想给您提供最简单的示例。)