How to remove an "mouseup" event listener in Java Script

Question

Here i am drag an element and droping in another place it works well if i don't use event listeners but if i use it in this format it is not performing "place" operation.

this link contains my code "with Event Listeners" Visit http://jsfiddle.net/vishwateja2000/wHprQ/2/

this link contains my code "without Event Listeners" Visit http://jsfiddle.net/vishwateja2000/W2Pgq/1/

document.getElementById("div2").addEventListener("mousedown", down);

function down(){
    t=1;
    document.getElementById("div1").addEventListener("mouseup", place);

    document.getElementById("div1").addEventListener("mousemove",function() {
        myFunction(event);
    });
}

function place(){ 
    document.getElementById("div1").removeEventListener("mousemove",function() {
         myFunction(event);
    });
}
function placeobj(x,y,x1,y1,l,r){
    var cpx = parseInt(x);
    var cpy = parseInt(y);
    var amtx=parseInt(x1);
    var amty=parseInt(y1);
    var of=10;
    document.getElementById("div2").style.left=cpx-amtx+l+"px";
    document.getElementById("div2").style.top=cpy-amty+r+"px";
}
function myFunction(e) {
    if(t==1){
        x1 = e.clientX;
        y1 = e.clientY;
        var el=document.getElementById('div2');
        l=el.offsetLeft;
        r=el.offsetTop;
        t=10;
    }
        x = e.clientX;
        y = e.clientY;
    placeobj(x,y,x1,y1,l,r);
}

Lior · Accepted Answer · 2014-07-31T08:06:09.373

The problem is that you used different functions when adding and removing the mousemove event. Although they have the same functionality they are different functions in memory and so are treated differently.

Take a look at the fixed version: http://jsfiddle.net/PN3TA/

The removeEventListener() has to have the same event name + function as used in the addEventListener() to remove the right event. The function can't be an anonymous function as that creates a new function (although it might look the same). You need to use a reference (like a pointer) which can be a named function or a variable.

NOTE: Also when passing a function to these methods you don't have to wrapped in an anonymous function if the original function expects to get the same arguments as the anonymous function. I mean, this:

 document.getElementById("div1").addEventListener("mousemove",function() {
    myFunction(event);
});

Could be written like this, because myFunction() expects an event argument which will be supplied anyway, saving you a function wrapper:

document.getElementById("div1").addEventListener("mousemove",  myFunction);

@JVT if you think this answer was helpful, you can also upvote it. :) — Lior, Aug 03 '14 at 13:55

score 0 · Answer 2 · answered Jul 31 '14 at 08:01

You've to attach an event with a reference to a function, then you can use the same reference to remove the listener. You can't remove anonymous event handlers with removeEventListener().

Attach with a reference:

document.getElementById("div1").addEventListener("mousemove", myFunction);

Remove with a reference:

document.getElementById("div1").removeEventListener("mousemove", myFunction);

Notice, that e is automatically passed to handler, you don't need to pass it manually.

score 0 · Answer 3 · answered Jul 31 '14 at 08:03

Dont use embedded event functions. Have named event functions. For example:

document.getElementById("div1").addEventListener("mouseup", myFunction);

myFunction(event){
if(t==1){
        x1 = e.clientX;
        y1 = e.clientY;
        var el=document.getElementById('div2');
        l=el.offsetLeft;
        r=el.offsetTop;
        t=10;
    }
        x = e.clientX;
        y = e.clientY;
    placeobj(x,y,x1,y1,l,r);
}

Now you can easily remove the event like this:

document.getElementById("div1").removeEventListener("mouseup", myFunction);

Also I would recommend using jQuery instead :)

How to remove an "mouseup" event listener in Java Script

3 Answers3

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