How to Effectively Remove JavaScript Event Listeners from Within Their Definitions?

Removing JavaScript Event Listeners within Listener Definitions

When trying to remove an event listener within its listener definition, JavaScript users may encounter challenges due to the context binding. This article demonstrates approaches to resolve this issue and effectively remove event listeners.

Approach 1: Using Named Functions

Instead of anonymous functions, define a named function and assign it to the event listener. This ensures that the function can be referenced later for removal.

var click_count = 0;

function myClick(event) {
    click_count++;
    if (click_count == 50) {
        // Remove the event listener
        canvas.removeEventListener('click', myClick);
    }
}

// Add the event listener
canvas.addEventListener('click', myClick);

Approach 2: Closure with Click Counter Variable

Closure allows the listener function to access variables defined outside its scope. In this case, encapsulate the click counter variable within the function.

var myClick = (function (click_count) {
    var handler = function (event) {
        click_count++;
        if (click_count == 50) {
            // Remove the event listener
            canvas.removeEventListener('click', handler);
        }
    };
    return handler;
})(0);

// Add the event listener
canvas.addEventListener('click', myClick);

Approach 3: Click Counter as Function Argument

If different elements need their own click counters, create a new function that takes the click counter as an argument.

var myClick = function (click_count) {
    var handler = function (event) {
        click_count++;
        if (click_count == 50) {
            // Remove the event listener
            canvas.removeEventListener('click', handler);
        }
    };
    return handler;
};

// Add the event listener
canvas.addEventListener('click', myClick(0));

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