<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="../js/jquery-3.5.1.js"></script>
    <script>
        //类名过滤
        //.hasclass()
        $(function () {
           $("li").each(function () {
               var bool = $(this).hasClass("select");
               if(bool)
               {
                   $(this).css("color","blue");
               }
           });
        });
    </script>
</head>
<body>
    <ul>
        <li>HTML</li>
        <li>CSS</li>
        <li>Javascript</li>
        <li class="select">jQuery</li>
        <li>Vue.js</li>
    </ul>
</body>
</html>