jquery event binding and release

jQuery is a very popular JavaScript library with a convenient API and powerful functions, and is widely used in Web front-end development. When using jQuery to develop front-end pages, it is often necessary to bind and unbind events to elements. This article will introduce in detail how to use jQuery for event binding and unbinding, and sort out common problems and their solutions.

1. Event binding

1. Binding a single event

JQuery can easily bind the event response function of an element. As shown below:

$(element).on(event, handler);

Among them, element is the element to which the event is bound, event is the bound event type, and handler is the event response function.

For example, if you want to add a click event to a button element, you can write like this:

$("button").on("click", function(){
    // 事件响应函数
});

2. Bind multiple events

If you want to bind multiple events to an element Events, you can add multiple event types in the on method. For example:

$(element).on(event1, event2, handler);

For example, if you want to bind click and mouseover events to a button element at the same time, you can write like this:

$("button").on("click mouseover", function(){
    // 事件响应函数
});

3. Bind event delegate

When When an event needs to be delegated to another element, you can use the event delegation function of the on method. Just specify the binding element as a selector. For example:

$(parentElement).on(event, childSelector, handler);

Among them, parentElement is the parent element to which the event is bound, childSelector is the child element selector to be delegated, and handler is the event response function.

For example, if you want to bind the click event delegate to the child element to the parent element, you can write like this:

$("#parent").on("click", "#child", function(){
    // 事件响应函数
});

2. Event cancellation

In page development, it is often Existing events need to be released to ensure that the code will not be executed repeatedly or problems will occur. jQuery provides three event release methods, namely off, unbind and die methods.

1.off method

The off method is mainly used to unblock events bound by the on method.

The following is the basic format of the off method:

$(element).off(event, handler);

Among them, element is the element of the event to be released, event is the event type to be released, and handler is the event response function to be released.

For example, assuming that a click event has been bound to the button element before, and now the event needs to be released, you can write like this:

$("button").off("click");

2.unbind method

unbind method It can also be used to unbind events, but it can unbind events through all methods.

The following is the basic format of the unbind method:

$(element).unbind(event, handler);

Among them, element is the element of the event to be released, event is the event type to be released, and handler is the event response function to be released.

For example, a click event was previously bound to the button element, and a mouse-up event was bound to the button element. Now you need to cancel both events. You can write like this:

$("button").unbind();

3.die method

The die method can unbind events through event delegation.

The following is the basic format of the die method:

$(parentElement).die(event, childSelector, handler);

Among them, parentElement is the parent element to be released, childSelector is the child element selector to be delegated, and handler is the event response function to be released. .

For example, if the click event delegate for the child element was previously bound to the parent element, and now the event needs to be released, you can write like this:

$("#parent").die("click", "#child");

3. Frequently Asked Questions and Solutions

1. How to prevent repeated binding of events?

Situation 1: If there are multiple events bound to the same element, you can use jquery's one method, which will only execute the event response function once.

For example:

$("button").one("click", function(){
    // 事件响应函数
});

Case 2: If an event needs to be bound multiple times, you can first use the off method to unbind the event.

For example:

function clickHandler(){
    // 事件响应函数
}
$("button").off("click", clickHandler).on("click", clickHandler);

Case 3: Use the unbind method to unbind the event before binding the event, and then rebind the event.

For example:

$("button").unbind("click").on("click", function(){
    // 事件响应函数
});

2. How to unbind an event through event delegation?

You can use the undelete or off method, both of which can release event delegation.

For example:

$("#parent").undelegate("#child", "click");
$("#parent").off("click", "#child");

3. How to cancel an anonymous event response function?

You can use the off method to define the event response function as a variable to unbind the event.

For example:

var clickHandler = function(){
    // 事件响应函数
}
$("button").on("click", clickHandler);
$("button").off("click", clickHandler);

This article introduces jQuery's event binding and unblocking methods as well as common problems and their solutions. How to use jQuery for event binding and unblocking is a necessary skill in front-end development. one. I hope that through studying this article, I can gain a deeper understanding of jQuery's event binding and unbinding, thereby improving the efficiency of Web front-end development.

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