jquery event implementation sequence

In front-end development, we often use jQuery to operate DOM elements and add various interactive effects to them, which is inseparable from the use of jQuery events. When using jQuery events, the order in which events are fired is very important, because the firing of one event may affect the execution of subsequent events. Therefore, this article will introduce the implementation sequence of jQuery events, hoping to help everyone better use jQuery events.

1. Event Binding

Before using jQuery events, you first need to bind events. There are two common methods of event binding:

1. Binding events through selectors

Code example:

$(selector).on(event,function)

This method can be done by selecting Use the handler to select DOM elements and bind events to the selected elements. For example:

$("button").on("click",function(){
    alert("您点击了按钮");
})

This code will select all elements and pop up a prompt box when the button is clicked.

2. Bind events directly

Code example:

$(dom).on(event,function)

This method can directly bind events to DOM elements without a selector. For example:

var btn = document.getElementById("btn");
$(btn).on("click",function(){
    alert("您点击了按钮");
})

This code binds a click event to a button with the ID "btn".

2. Event triggering sequence

After binding the event, when the event is triggered, jQuery will execute the event in a certain order. The specific event triggering sequence is as follows:

1. Capture phase

Before the event bubbles up to the target element, jQuery will first traverse down the top of the DOM tree, looking for The event target is related to the node and executes the event handler associated with it. This process is called the "capture phase".

2. Target event execution

When the event target is found, jQuery will execute the event processing function related to it.

3. Bubble stage

After executing the event handler of the target element, jQuery will bubble up along the DOM tree and execute the parent elements related to the event one by one. event handling function. This process is called the "bubbling phase".

It should be noted that jQuery events can use the event.stopPropagation() method to prevent the event from bubbling, and the event.preventDefault() method can also be used to cancel the default behavior of the event.

3. Event delegation

Event delegation is also a very common technique when using jQuery events. Through event delegation, you can bind event handlers to a parent element, thereby avoiding binding the same event handler to each child element. For example:

$("#parent").on("click","button",function(){
    alert("您点击了按钮");
})

This code binds a click event to a parent element with the ID "parent". When a element is clicked on the parent element, a prompt box will pop up.

In event delegation, the event will be triggered on the parent element, and then jQuery will traverse the child elements under the parent element to find the node related to the event target and execute the event handling function related to it. Therefore, when using event delegation, the order in which events are fired also follows the order described above.

4. Summary

This article introduces the implementation sequence of jQuery events, including event binding, event triggering sequence and event delegation. When using jQuery events, we need to pay attention to the order in which events are triggered to ensure correct execution of events. I hope this article can be helpful to everyone in their work in front-end development.

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