Web Front-endJS TutorialPractical Tips: Event Bubbling to Improve Web Page Intelligence and Efficiency
Event bubbling skills: Make your web page smarter and more efficient, specific code examples are needed
Event bubbling is an important concept in JavaScript, it can Let us process multiple elements in web pages more conveniently and efficiently. In this article, we will introduce what event bubbling is, why to use event bubbling, and how to implement event bubbling in code.
- What is event bubbling?
When there are multiple elements nested together in a page, and each element is bound to the same event handling function, when the event is triggered, the event will be triggered from the innermost element Start and then work your way up to the outermost element. This method of event delivery is called event bubbling. In short, event bubbling is the process of propagating events from the inside out.
- Why use event bubbling?
Using event bubbling has the following benefits:
2.1 More efficient
When we have a large number of elements on the page that need to be bound to the same event processing When using functions, using event bubbling can reduce the amount of duplicate code and improve code reusability and maintainability.
2.2 Smarter
Event bubbling allows us to uniformly manage the events of child elements on the parent element. By monitoring the parent element, we can selectively process them according to actual needs. A specific child element.
2.3 Easier
Using event bubbling can avoid the trouble of rebinding event handlers when adding or removing elements dynamically. Because event bubbling is delivered based on the element's hierarchical structure, no matter whether the element exists when the page is loaded or is dynamically generated later, we only need to bind the event handler to its parent element.
- How to implement event bubbling?
In JavaScript, we can bind event processing functions to elements through the addEventListener method, and obtain the target element of the event through the target attribute in the event object. Then, we can obtain the parent element through the parentNode attribute of the target element to achieve event bubbling.
The following is a specific code example that demonstrates how to use event bubbling to change the background color of a child element when its parent element is clicked:
<!DOCTYPE html>
<html>
<head>
<style>
.parent {
width: 200px;
height: 200px;
background-color: #f3f3f3;
}
.child {
width: 100px;
height: 100px;
background-color: #ccc;
}
</style>
</head>
<body>
<div class="parent">
<div class="child"></div>
<div class="child"></div>
</div>
<script>
const parent = document.querySelector('.parent');
parent.addEventListener('click', function(event) {
if (event.target.classList.contains('child')) {
event.target.parentNode.style.backgroundColor = 'red';
}
});
</script>
</body>
</html>In the above code, we first The DOM objects of the parent element and child element are obtained through the querySelector method, and then the click event handler is bound to the parent element using the addEventListener method. In the processing function, use the target attribute of the event object to determine whether the click is a child element. If so, obtain its parent element through the parentNode attribute and change its background color to red.
Through this example, we can see that we only need to bind the event handler function to the parent element to change the background color of the parent element when the child element is clicked, which greatly simplifies the writing and maintenance of code. .
By learning and using event bubbling techniques, we can make web pages more intelligent and efficient. Not only can it reduce code duplication and improve code reusability and maintainability, it can also make it easier to manage dynamically generated elements. I hope this article will help you learn and master event bubbling!
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