JavaScript：删除事件侦听器 [英] JavaScript: remove event listener

问题描述

  canvas.addEventListener（'click'， function（event）{
 click ++; 
 if（click == 50）{
 //在此处删除此事件侦听器
} 
 //这里有更多的代码。 
  

我该怎么做？= = ...
谢谢。

解决方案

您需要使用命名函数。

另外，
函数myClick（event）{
click_count ++;
if（click_count == 50）{
//删除
canvas.removeEventListener （'click'，myClick）;
}
}

//添加
canvas.addEventListener（'click'，myClick）;

---

编辑： code> click_cou nter 这样的变量：

  var myClick =（function（click_count）{
 var handler = function（event）{
 click_count ++; 
 if（click_count == 50）{
 //删除
 canvas.removeEventListener（'click'，handler）; 
} 
}; 
 return handler; 
}）（0）; 
 
 //添加
 canvas.addEventListener（'click'，myClick）; 
  

这样，您可以跨多个元素递增计数器。

---

如果你不想要，并希望每个人都有自己的计数器，那么这样做： p>

  var myClick = function（click_count）{
 var handler = function（event）{
 click_count ++; 
 if（click_count == 50）{
 //删除
 canvas.removeEventListener（'click'，handler）; 
} 
}; 
 return handler; 
}; 
 
 //添加
 canvas.addEventListener（'click'，myClick（0））; 
  

编辑： 我忘记将正在返回的处理程序命名在最后两个版本。

I'm trying to remove an event listener inside of a listener definition:

canvas.addEventListener('click', function(event) {
    click++;
    if(click == 50) {
        // remove this event listener here!
    }
// More code here ...

How could I do that? this = event... Thank you.

解决方案

You need to use named functions.

Also, the click variable needs to be outside the handler to increment.

var click_count = 0;

function myClick(event) {
    click_count++;
    if(click_count == 50) {
       // to remove
       canvas.removeEventListener('click', myClick);
    }
}

// to add
canvas.addEventListener('click', myClick);

---

EDIT: You could close around the click_counter variable like this:

var myClick = (function( click_count ) {
    var handler = function(event) {
        click_count++;
        if(click_count == 50) {
           // to remove
           canvas.removeEventListener('click', handler);
        }
    };
    return handler;
})( 0 );

// to add
canvas.addEventListener('click', myClick);

This way you can increment the counter across several elements.

---

If you don't want that, and want each one to have its own counter, then do this:

var myClick = function( click_count ) {
    var handler = function(event) {
        click_count++;
        if(click_count == 50) {
           // to remove
           canvas.removeEventListener('click', handler);
        }
    };
    return handler;
};

// to add
canvas.addEventListener('click', myClick( 0 ));

EDIT: I had forgotten to name the handler being returned in the last two versions. Fixed.

这篇关于JavaScript：删除事件侦听器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IT屋！