如何使用“setTimeout”调用对象本身

问题描述

为什么我不能在javascript对象中使用 setTimeout ？

Why can't I use setTimeout in a javascript object?

Message = function () {

    ...
    ...        

    this.messageFactory = ...
    this.feedbackTag = document.getElementById('feedbackMessages');

    this.addInfo = function (message) {
        var info = this.messageFactory.createInfo(message); // create a div
        this.feedbackTag.appendChild(info);

        setTimeout('this.feedbackTag.removeChild(info)', 5000);
        // why in here, it complain this.feedbacktag is undefined ??????

    };
}

感谢Steve的解决方案，现在如果代码为低于...
，因为'this'之前实际上是指向setTimeOut中的函数，它无法重新发送消息。

Thanks for Steve`s Solution, now it will work if the code is as below...because the 'this' before was actually pointing to the function within setTimeOut, it cannot rearch Message.

Message = function () {

    ...
    ...        

    this.messageFactory = ...
    this.feedbackTag = document.getElementById('feedbackMessages');

    this.addInfo = function (message) {
        var info = this.messageFactory.createInfo(message); // create a div
        this.feedbackTag.appendChild(info);

        var _this = this;
        setTimeout(function() { _this.feedbackTag.removeChild(info); }, 5000);

    };
}

但是如果我们这样做，为什么它不起作用：

But why doesn`t it work if we do this:

Message = function () {

    ...
    ...        

    this.messageFactory = ...
    this.feedbackTag = document.getElementById('feedbackMessages');
    // public function
    this.addInfo = function (message) {
        var info = this.messageFactory.createInfo(message); // create a div
        this.feedbackTag.appendChild(info);

        delayRemove(info);

    };
    // private function
    function delayRemove(obj) {
        var _this = this;
        setTimeout(function() { _this.feedbackTag.removeChild(info); }, 5000);
    }
}

推荐答案

尝试替换此行：

setTimeout('this.feedbackTag.removeChild(info)', 5000);

这两行：

var _this = this;
setTimeout(function() { _this.feedbackTag.removeChild(info); }, 5000);

注意：

永远不要通过一个字符串，因为它调用 eval （你应该只在必要时使用它）。而是通过功能引用（这可以是匿名函数）。

Never pass setTimeout a string, as this invokes eval (which you should only use when necessary). Instead, pass setTimeout a function reference (this can be an anonymous function).

最后，始终检查 this 关键字是否指向什么你认为它指向（参见） 。

Finally, always check that the this keyword is pointing to what you think it points to (see http://www.alistapart.com/articles/getoutbindingsituations).

解决问题2：

我认为对于正常功能，此设置为窗口对象 - 无论它们在何处被声明。因此，将代码移动到单独的函数中无法解决问题。

I believe that for normal functions, this is set to the window object—regardless of where they are declared. So moving the code into a separate function wouldn't fix the problem.

这篇关于如何使用“setTimeout”调用对象本身的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！