为什么此Javascript方法不会继续调用自身? [英] Why won't this Javascript method keep calling itself?

问题描述

我有一个具有特权方法的JavaScript对象.当此方法完成后，我希望它可以自我调用(经过一小段超时后)，并无限期地继续运行.不幸的是，该方法仅运行两次，然后停止运行而没有任何错误(在Chrome和IE中测试，结果相同).

I have a JavaScript object with a privileged method. When this method has completed, I would like it to call itself (after a small timeout) and continue running indefinitely. Unfortunately, the method only runs twice, then it stops without any error (tested in Chrome and IE with the same results).

代码如下:

function Test() {
    // ... private variables that testMethod needs to access ...
    this.testMethod = function() {
        alert("Hello, from the method.");
        setTimeout(this.testMethod, 2000);
    };
}

var myTest = new Test();
myTest.testMethod();

我希望每两秒钟收到一次警报，但是相反，它只显示两次警报，然后停止.您可以在此处看到在线示例.知道为什么会这样吗?

I would expect to get the alert every two seconds, but instead it only shows the alert twice, then stops. You can see a live example here. Any idea why this would be happening?

推荐答案

首次使用"myTest.testMethod();"进行调用时"this"关键字绑定到"myTest"对象，当超时触发时，"window"对象绑定到"this"关键字，而"this.testMethod"等效于"window.testMethod".试试:

When you first call it with "myTest.testMethod();" the "this" keyword is bond to your "myTest" object, when the timeout fires the "window" object is bond to "this" keyword and "this.testMethod" is equivalent to "window.testMethod". Try:

function Test() {
    // ... private variables that testMethod needs to access ...
    this.testMethod = function() {
        alert("Hello, from the method.");
        setTimeout((function(self){
            return function(){self.testMethod();};
        })(this), 2000);
    };
}

var myTest = new Test();
myTest.testMethod();

或者:

function Test() {
    // ... private variables that testMethod needs to access ...
    this.testMethod = function() {
        alert("Hello, from the method.");
        var self = this;
        setTimeout(function(){self.testMethod();}, 2000);
    };
}

var myTest = new Test();
myTest.testMethod();

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