How do I add and remove an event listener using a function with parameters?
Solution 1
Have you tried maintaining a reference to the anonymous function (like you suggested)?
So:
var listener = function() {
check_pos(box);
};
window.addEventListener('scroll', listener, false);
...
window.removeEventListener('scroll', listener, false);
Mozilla's docs suggest the same thing.
Solution 2
var listener;
listener = function(){
if( window.target != anotherEvent.target )
{
...CODE where
window.removeEventListener('click', listener , false);
};
window.addEventListener('click', listener ,false);
Comments
-
Bungle almost 2 years
Sorry if this is a common question, but I couldn't find any answers that seemed pertinent through searching.
If I attach an event listener like this:
window.addEventListener('scroll', function() { check_pos(box); }, false);
it doesn't seem to work to try to remove it later, like this:
window.removeEventListener('scroll', function() { check_pos(box); }, false);
I assume this is because the
addEventListener
andremoveEventListener
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.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 thescroll
event once for each<iframe>
that I have (the quantity varies), and once thecheck_pos()
function measures a certain position, it will call another function and also remove the event listener to free up system resources.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.
Hope that makes sense.
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Bungle almost 14 yearsThanks, Vivin - correct me if I'm wrong, but I don't think this would allow me to set up multiple event listeners with different values for "box," which is what I need to do. The argument "box" isn't a global variable. For example, just using literal values, I might call
window.addEventListener('scroll', function() { do_something('string1'); }, false);
and laterwindow.removeEventListener('scroll', function() { do_something('string1'); }, false);
and laterwindow.addEventListener('scroll', function() { do_something('string2'); }, false);
, etc. -
Vivin Paliath almost 14 yearsThere is a way to add multiple event listeners by using closures (See stackoverflow.com/questions/2276961/…). However I'd suggest using jQuery if you want to do some serious event-handling. It makes it much easier.
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Ambuj Khanna about 6 yearsIf remove it by using < window.removeEventListener('scroll', listener, false); > and check again by using < "listener" in window" > so it is still giving me back "true". Any help?