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。
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.
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.
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