javascript - js对象的方法中引用自身对象，无法找到对象？

Question

一个“秒表”对象，我将他放入jquery的$(function(){})中，整个JS文件代码如下： {代码...} 问题来了：点击此DOM对象后，代码错误提示我在setTimeout('StopWatch.start()', 10);这句代码里没有找到StopWatch对象。...

PHP中文网 · Answer

setTimeout('StopWatch.start()', 10);
传递字符串给setTimeout函数时，JS引擎会把字符串使用Function构造函数将其转换为函数对象，
使用new Function创建的函数没有闭包作用域的~~
StopWatch会直接在全局作用域下找

setTimeout(new Function('StopWatch.start();'), 10);

Functions created with the Function constructor do not create closures to their creation contexts; they always are created in the global scope. When running them, they will only be able to access their own local variables and global ones, not the ones from the scope in which the Function constructor was called. This is different from using eval with code for a function expression.

通过下面的代码可以更清楚写:
全部输出global

(function(){
    var foo={
        name:'foo',
        testFun:function(){
            console.log(this.name);
        }
    }
    
    setTimeout('foo.testFun();', 10);
}());

var foo={
    name:'global',
    testFun:function(){
        console.log(this.name);
    }
}

setTimeout('foo.testFun();', 10);

针对你的问题的解决方法,供参考：
1.

    var __that__=this;
    if(!this.started){
        this.stopWatchTimeSet = setTimeout(function(){
            __that__.start()
        }, 10);
    }

2.

    if(!this.started){
        this.stopWatchTimeSet = setTimeout(this.start.bind(this), 10);
    }