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How to determine whether a tag exists in jquery

青灯夜游

Release： 2022-06-07 17:38:48

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Judgment method: 1. Use the element selector to select the specified tag element. The syntax "$("tag name")" will return a jQuery object containing the specified tag; 2. Use the length attribute to determine whether the jQuery object is Is empty, the syntax is "object.length!=0", if true is returned, it exists, otherwise it does not exist.

How to determine whether a tag exists in jquery

The operating environment of this tutorial: windows7 system, jquery3.2.1 version, Dell G3 computer.

jquery method to determine whether a tag exists

##1. Use the jQuery element selector to select the specified element tag

The jQuery element selector selects elements based on their name.

$("标签名")

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For example,

$("p") is to select the

tag element.

Will return a jQuery object containing the specified element.

2. Use the length attribute to determine whether the jQuery object is empty.

The length attribute can get the length of the jQuery object; then you can check whether the length is 0. Determine whether the object is empty.

jQuery对象.length!=0

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If it is not empty (the return value is true), the specified tag exists
If it is empty (the return value is false), Then the specified tag does not exist

Implementation example: Determine whether the p element tag and span element tag exist

<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<style>
			.siblings,.siblings *{ 
				display: block;
				border: 2px solid lightgrey;
				color: lightgrey;
				padding: 5px;
				margin: 15px;
			}
			#border{
				border: 2px solid pink;
			}
		</style>
		<script src="js/jquery-3.2.1.min.js"></script>
		<script type="text/javascript">
			$(document).ready(function() {
				$("button").click(function() {
					var len1=$("p").length;
					var len2=$("span").length;
					if(len1!=0){
						console.log("p元素存在")
					}else{
						console.log("p元素不存在")
					}
					if(len2!=0){
						console.log("span元素存在")
					}else{
						console.log("span元素不存在")
					}
				});
			});
		</script>
	</head>
	<body>
		<div class="siblings">div元素
			<p>p（p元素）</p>
			<h2>h2（h2元素）</h2>
			<h3>h3（h3元素）</h3>
			<p>p（p元素）</p>
		</div>
		<button>检查p元素和span元素是否存在</button>
	</body>
</html>

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How to determine whether a tag exists in jquery

It can be seen that in the above example, the p element tag exists, but the span element tag does not exist.

[Recommended learning:

jQuery video tutorial, web front-end video]

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