Live cannot be used in jquery

In recent years, the field of front-end development has developed rapidly, and frameworks and libraries have emerged one after another. Among them, jQuery is still one of the most representative and influential JS libraries. However, even though jQuery has become an indispensable tool in the development world, there are still some situations where we encounter difficulties, such as the live() function in jQuery not working. This article will explore why the live() function in jQuery cannot be used and give solutions.

1. The role of live()

Before jQuery 1.3, we could only operate DOM elements by binding events, which would be bound once to each element to be operated. Events, if there are too many elements, doing so will greatly reduce performance. Version 1.3 of jQuery introduced the live() function, which can bind events to all elements that match the selector. Events can also be automatically triggered when newly added elements match this selector, thus solving the problem of large-scale operations on elements. performance issues.

2. Defects of live()

The live() function is indeed very powerful, but it also has some defects that make it unusable. When we try to use the live() function in jQuery 1.9 and later versions, we will find that it has been removed. The latest version of jQuery no longer has the live() function. This is because the implementation of the live() function is not elegant enough. It uses some special techniques to simulate the effects of event bubbling and proxy events, causing it to conflict with other jQuery functions.

In addition, in addition to jQuery technically announcing that live() is no longer supported, starting from HTML5, the new on() method has been introduced to replace bind(), live(), delegate( ) and other methods, which means that in modern web development, using live() no longer makes much sense.

3. Solution

1. Use delegate() function

delegate() function is an alternative method provided by jQuery for transferring events Delegate processing to the parent element. Use the selector to specify the element to which the event is bound, and bind the event to its ancestor element. In this way, when jQuery executes the event, it will check whether the ancestor element of the currently selected element matches the selector. If it matches, the function will be executed. This method does not encounter problems when events are dynamically added, and it plays in a loop, similar to live().

The usage method is as follows:

$(selector).delegate(childSelector,event,data,function)

selector: The parent element used for delegate processing.
childSelector: The child element that needs to be processed.
event: event type, such as click.
data: Data passed into the event handler.
function: The callback function executed when the event is triggered.

The sample code is as follows:

$(function(){

$("body").delegate(".btn", "click", function(){
    console.log("click btn!");
})

})

2. Use on() function

The on() function is an event processing function provided since version 1.9 of jQuery. The bound event can not only listen to DOM events, but also listen to custom events. jQuery recommends using on() instead of the previous bind(), live() and delegate() functions, and on() is the recommended method, which can achieve almost all the functions of the live() function.

The usage method is as follows:

$(selector).on(event,childSelector,data,function)

selector: The element to be bound to the event.
event: event type, such as click.
childSelector: Child element selector, used to automatically bind events when dynamically loading child elements.
data: Data passed to the event handler, can be empty.
function: The callback function executed when triggered.

The sample code is as follows:

$(function(){

$("body").on("click", ".btn", function(){
    console.log("click btn!");
})

})

4. Summary

Through the introduction of this article and sample code, we can see that although the live() function cannot be used, we can use the delegate() and on() functions to achieve the same effect and continue to use jQuery. In modern web development, with the continuous advancement of browsers and front-end related technologies, we should try to avoid using outdated methods and functions and use the latest technologies and methods as much as possible to improve development efficiency and code quality.

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