How Can I Safely Remove JavaScript Event Listeners Inside Their Own Handlers?-JS Tutorial-php.cn

How Can I Safely Remove JavaScript Event Listeners Inside Their Own Handlers?

Barbara Streisand

Release： 2024-12-07 14:51:12

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How Can I Safely Remove JavaScript Event Listeners Inside Their Own Handlers?

Removing JavaScript Event Listeners within Event Handlers

In JavaScript, removing an event listener within the same event handler's definition can pose challenges. To address this, consider the following strategies:

Using Named Functions

One approach involves using named functions:

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);

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Closure with Indirect Event Handling

Alternatively, you can close over the click counter using an indirect event handling pattern:

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);

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Using a Function Generator

If you need each element to have its own counter, you can use a function generator:

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));

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