如何使用带有参数的函数添加和删除事件侦听器？ [英] How do I add and remove an event listener using a function with parameters?

问题描述

很抱歉，如果这是一个常见问题，但我找不到通过搜索找到的相关答案。

Sorry if this is a common question, but I couldn't find any answers that seemed pertinent through searching.

如果我附加了这样的事件侦听器，则： / p>

If I attach an event listener like this:

window.addEventListener('scroll', function() { check_pos(box); }, false);

稍后尝试删除它似乎不起作用，像这样：

it doesn't seem to work to try to remove it later, like this:

window.removeEventListener('scroll', function() { check_pos(box); }, false);

我认为这是因为 addEventListener 和 removeEventListener 方法想要引用相同的函数，而我为它们提供了匿名函数，尽管它们在代码上相同，但实际上并不相同。

I assume this is because the addEventListener and removeEventListener methods want a reference to the same function, while I've provided them with anonymous functions, which, while identical in code, are not literally the same.

如何更改代码以使对 removeEventListener 的调用正常工作？ box参数是指我在屏幕上跟踪的< iframe> 的名称；也就是说，我希望能够为每个拥有的< iframe> 预订一次 scroll 事件（数量会有所不同），一旦 check_pos（）函数测量到某个位置后，它将调用另一个函数，并删除事件侦听器以释放系统资源。

How can I change my code to get the call to removeEventListener to work? The "box" argument refers to the name of an <iframe> that I'm tracking on the screen; that is, I want to be able to subscribe to the scroll event once for each <iframe> that I have (the quantity varies), and once the check_pos() function measures a certain position, it will call another function and also remove the event listener to free up system resources.

我的直觉是该解决方案将涉及到闭包和/或命名匿名函数，但我不确定到底是什么样，并希望举一个具体的例子。

My hunch is that the solution will involve a closure and/or naming the anonymous function, but I'm not sure exactly what that looks like, and would appreciate a concrete example.

希望如此。

推荐答案

您是否尝试过维护对匿名函数的引用（如您建议的那样）？

Have you tried maintaining a reference to the anonymous function (like you suggested)?

所以：

var listener = function() {
  check_pos(box);
};

window.addEventListener('scroll', listener, false);
...
window.removeEventListener('scroll', listener, false);

Mozilla的文档建议同一件事。

Mozilla's docs suggest the same thing.

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