为什么这个Javascript方法不会自己调用？ [英] Why won't this Javascript method keep calling itself?

问题描述

我有一个带有特权方法的JavaScript对象。当这个方法完成后，我希望它自己调用（在一个小的超时后）并继续无限期地运行。不幸的是，该方法只运行两次，然后停止没有任何错误（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，但它只显示警报两次，然后停止。您可以在此处查看实时示例。知道为什么会发生这种情况吗？

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

当你第一次用myTest.testMethod（）;调用它时this关键字绑定到myTest对象，当超时触发window对象绑定到this关键字时，this.testMethod等同于window.testMethod。
尝试：

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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