JavaScript:删除事件监听器
我正在尝试删除侦听器定义中的事件侦听器:
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 ...
我怎么能这样做?这 = 事件...
How could I do that? this = event...
推荐答案
你需要使用命名函数.
另外,click
变量需要在处理程序之外才能递增.
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);
<小时>
您可以像这样关闭 click_counter
变量:
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);
通过这种方式,您可以跨多个元素递增计数器.
This way you can increment the counter across several elements.
如果您不希望这样,并且希望每个人都有自己的计数器,那么请执行以下操作:
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 ));
我忘记命名在最后两个版本中返回的处理程序.已修复.
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