JavaScript: remove 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... Thank you.

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);

---

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.