How to determine if an element is a child element of another element in jquery-Front-end Q&A-php.cn

How to determine if an element is a child element of another element in jquery

青灯夜游

Release： 2022-11-07 19:10:09

Original

2191 people have browsed it

Two methods: 1. Use the children() and length attributes to judge. The syntax is "specified element object.children (specified child element object).length==0". If the return value is true, it does not exist. , and vice versa. 2. Use find() and length attributes to judge. The syntax is "specified element object.find(specified sub-element object).length==0". If the return value is true, it does not exist, otherwise it exists.

How to determine if an element is a child element of another element in jquery

The operating environment of this tutorial: windows7 system, jquery3.6.1 version, Dell G3 computer.

To determine whether an element is a child element of another element is to determine whether a child element of an element is another specified element.

In jquery, there are two ways to find child elements:

children() method: Get the direct subset elements under the element
find() method: Get all subset elements (including subsets of subsets) under the element

Therefore, these two methods can be used to determine Whether an element is a child of another element.

Method 1: Use the children() and length attributes to determine

The children() method returns all direct child elements of the selected element. .

The syntax used to determine whether the specified child element B exists in the specified element A:

A.children(B).length==0

Copy after login

A.children(B), will be returned All direct child elements of A element B object collection
Object collection.length==0, determine whether the object collection is 0, if it is 0, it does not exist, On the contrary, there is

Example:

<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<script src="js/jquery-3.6.1.min.js"></script>
		<style>
			div * {
				display: block;
				border: 2px solid lightgrey;
				color: lightgrey;
				padding: 5px;
				margin: 15px;
			}
		</style>

		<script>
			$(document).ready(function() {
				$("button").on("click", function() {
					$("ul").children("#box").css({
						"color": "red",
						"border": "2px solid red"
					});
					var number =$("ul").children("#box").length;
					console.log(number);
					if (number == 0) {
						  console.log("不含");
					}else{
					     console.log("含有");
					}
				});
			});
		</script>
	</head>

	<body class="ancestors">
		<div style="width:500px;">div (父节点)
			<ul>ul (指定元素)
				<li id="box">li (子节点1)
					<span>span (孙节点1)</span>
				</li>
				<li>li (子节点2)
					<span>span (孙节点2)</span>
				</li>
				<li>li (子节点3)
					<span>span (孙节点3)</span>
				</li>
			</ul>
		</div>
		<button>选取ul的所有子元素#box</button>
	</body>

</html>

Copy after login

How to determine if an element is a child element of another element in jquery

##Method 2: Use find() and length attributes Determination

The find() method obtains the descendants of each element in the current element collection, filtered by selectors, jQuery objects, or elements.

Judgment syntax:

A.find(B).length==0

Copy after login

The syntax meaning is actually similar to method 1, you can refer to it.

Example:

<script>
	$(document).ready(function() {
		$("button").on("click", function() {
			$("ul").find("#box").css({
				"color": "red",
				"border": "2px solid red"
			});
			var number =$("ul").find("#box").length;
			console.log(number);
			if (number == 0) {
				  console.log("不含");
			}else{
				 console.log("含有");
			}
		});
	});
</script>

Copy after login

How to determine if an element is a child element of another element in jquery

[Recommended learning:

jQuery video tutorial, web front-end video 】

The above is the detailed content of How to determine if an element is a child element of another element in jquery. For more information, please follow other related articles on the PHP Chinese website!