How can I remove a JavaScript event listener?

Question

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...

Answer 1

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);

---

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 ));

Answer 2

   canvas.addEventListener('click', function(event) {
      click++;
      if(click == 50) {
          this.removeEventListener('click',arguments.callee,false);
      }

Should do it.

Answer 3

You could use a named function expression (in this case the function is named abc), like so:

let click = 0;
canvas.addEventListener('click', function abc(event) {
    click++;
    if (click >= 50) {
        // remove event listener function `abc`
        canvas.removeEventListener('click', abc);
    }
    // More code here ...
}

Quick and dirty working example: http://jsfiddle.net/8qvdmLz5/2/.

More information about named function expressions: http://kangax.github.io/nfe/.

Answer 4

If @Cybernate's solution doesn't work, try breaking the trigger off in to it's own function so you can reference it.

clickHandler = function(event){
  if (click++ == 49)
    canvas.removeEventListener('click',clickHandler);
}
canvas.addEventListener('click',clickHandler);

Answer 5

element.querySelector('.addDoor').onEvent('click', function (e) { });
element.querySelector('.addDoor').removeListeners();


HTMLElement.prototype.onEvent = function (eventType, callBack, useCapture) {
this.addEventListener(eventType, callBack, useCapture);
if (!this.myListeners) {
    this.myListeners = [];
};
this.myListeners.push({ eType: eventType, callBack: callBack });
return this;
};


HTMLElement.prototype.removeListeners = function () {
if (this.myListeners) {
    for (var i = 0; i < this.myListeners.length; i++) {
        this.removeEventListener(this.myListeners[i].eType, this.myListeners[i].callBack);
    };
   delete this.myListeners;
};
};

Answer 6

It looks like no one's covered the part of the current JavaScript DOM specification that gives you a mechanism to remove your event listener without using removeEventListener. If we look at https://dom.spec.whatwg.org/#concept-event-listener we see that there are a number of properties that can be passed to control event listening:

{
  type (a string)
  callback (null or an EventListener object)
  capture (a boolean, initially false)
  passive (a boolean, initially false)
  once (a boolean, initially false)
  signal (null or an AbortSignal object)
  removed (a boolean for bookkeeping purposes, initially false) 
}

Now, there's a lot of useful properties in that list, but for the purposes of removing an event listener it's the signal property that we want to make use of (which was added to the DOM level 3 in late 2020), because it lets us tell the JS engine to remove an event listener by just calling abort() instead of having to bother with removeEventListener:

const canvasListener = (new AbortController()).signal;

canvas.addEventListener('click', () => {
  click++;
  if (click === 50) {
    canvasListener.abort();
  } else {
    doSomethingWith(click);
  }
}, {
  signal: canvasListener 
});

(Note that this does not use the useCapture flag, because the useCapture flag is essentially completely useless)

And done: the JS engine will abort and clean up our event listener. No keeping a reference to the handling function, no making sure we call removeEventListener with the exact same properties as we called addEventListener: we just cancel the listener.

Answer 7

If someone uses jquery, he can do it like this :

var click_count = 0;
$( "canvas" ).bind( "click", function( event ) {
    //do whatever you want
    click_count++;
    if ( click_count == 50 ) {
        //remove the event
        $( this ).unbind( event );
    }
});

Hope that it can help someone. Note that the answer given by @user113716 work nicely :)

Answer 8

I think you may need to define the handler function ahead of time, like so:

var myHandler = function(event) {
    click++; 
    if(click == 50) { 
        this.removeEventListener('click', myHandler);
    } 
}
canvas.addEventListener('click', myHandler);

This will allow you to remove the handler by name from within itself.

Answer 9

A way to achieve that is use jquery, so you can use:

canvas.click(yourfunction);

then you can detach all event listener with:

canvas.off();

Answer 10

Try this, it worked for me.

<button id="btn">Click</button>
<script>
 console.log(btn)
 let f;
 btn.addEventListener('click', f=function(event) {
 console.log('Click')
 console.log(f)
 this.removeEventListener('click',f)
 console.log('Event removed')
})  
</script>