How to determine whether a certain attribute is included in jquery-Front-end Q&A-php.cn

How to determine whether a certain attribute is included in jquery

青灯夜游

Release： 2022-12-16 18:43:38

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Implementation steps: 1. Use the jquery selector to obtain the specified element object, the syntax "$(selector)"; 2. Use the attr() method to obtain the attribute value of the specified attribute of the jquery object, the syntax "element object" .attr("attribute name")"; 3. Use the "==" operator to determine whether the obtained attribute value is equal to undefined. The syntax is "attribute value =='undefined'". If it is equal, an attribute will not be included, otherwise it will be included. .

How to determine whether a certain attribute is included in jquery

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

In jquery, to determine whether an element has a certain attribute, the attr() method is mainly used. Through this method, the obtained attribute value can be judged to determine whether the element has a certain attribute.

Implementation steps:

Step 1: Use jquery selector to obtain the specified element object

$(selector)

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Will return a jquery object containing the specified element

Step 2: Use the attr() method to obtain the value of the specified attribute of the jquery object

元素对象.attr("属性名")

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Will return the attribute value of the specified attribute

Step 3: Use the "==" operator to determine whether the obtained attribute value is equal to undefined

属性值==&#39;undefined&#39;

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If equal, then do not include a certain attribute
If not equal, then include a certain attribute

Implementation example:

Determine whether the input element has a name attribute

<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8" />
        <script src="js/jquery-3.6.0.min.js"></script>
        <script>
            $(document).ready(function() {
                $("button").click(function() {
                    var value=$("input").attr("name");
					if(value==&#39;undefined&#39;){
						console.log("不包含name属性")
					}
					else{
						console.log("包含name属性")
					}
                });
            });
        </script>
    </head>
    <body>
        <form action="form_action.asp" method="get">
          <p>name：<input type="text" name="fullname" /></p>
          <p>email：<input type="text" name="email" /></p>
        </form>
        <button>判断input元素是否有name属性</button>
    </body>
</html>

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How to determine whether a certain attribute is included in jquery

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