jQuery remove live listener

When developing web applications, it is very common to use a custom event dispatcher and add listeners. jQuery is a very popular JavaScript library with a very powerful event system that allows developers to add listeners to DOM elements and handle events triggered by DOM elements. Using these event listeners, we can perform some actions, such as sending AJAX requests, pushing data to the server, etc.

However, developers also need to know how to properly remove listeners from DOM elements. This article will introduce how to delete live listeners using jQuery.

Prior to jQuery 1.7, you needed to use the live() method to add event listeners. The sample code is as follows:

$('a').live('click', function() {
    console.log('clicked');
});

This code block adds a listener. When the a element is clicked, a message will be printed in the console.

Now suppose that at some point we want to remove the listener from the a element, what should we do?

In jQuery, when you want to delete a listener, you can use the unbind() method and specify the corresponding event type and handler function. But here, this approach doesn't work. The reason is that the listener added by the live() method is not actually on the DOM element itself, but is implemented throughout the document.

So if you try to use the unbind() method to remove the live event listener, it will not work properly. In other words, this event listener will exist until the page is closed or reloaded.

In order to solve this problem, the jQuery team developed a new method delegate(), which can be used to replace live(). Listeners added using the delegate() method can be removed using the off() method.

The following is new code that uses the delegate() method to rewrite the previous code example:

$(document).delegate('a', 'click', function() {
    console.log('clicked');
});

Here, we use the delegate() method to add an event listener. The first parameter is the selector, specifying the element to be monitored, the second parameter is the specified event type, and the third parameter is the event handling function.

Now, if you want to delete this event listener at some point, you can use the off() method, as shown below:

$(document).off('click', 'a', function() {
    console.log('clicked');
});

In this new code block, we pass off() Method to clear the listener. The first parameter is the event type, the second parameter is the selector, and the third parameter is the event handler to be removed. Note that the event handler must match exactly, as you cannot just remove a specific listener that a selector is attached to.

The click event itself on the element will not be changed here, but the event listener will be deleted on the entire page. Therefore, if you want to add a new live event listener in the future, you only need to use the new delegate() method to add the listener without worrying about the impact of the old listener on the new listener.

Summary

In this article, we learned how to delete live listeners in jQuery. When you add an event listener using jQuery, it is attached to the entire document rather than a specific DOM element. Therefore, in order to remove this type of listener, you need to use the delegate() method instead of the live() method, and use the off() method to remove the corresponding listener. If you want to prevent other types of event listeners from being deleted, be sure to use the correct syntax to ensure that only the specified listeners you want to be deleted are deleted.

The above is the detailed content of jQuery remove live listener. For more information, please follow other related articles on the PHP Chinese website!