1.helloworld.html

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>1.helloworld</title>

    <style>
        body {
            padding: 50px;
        }

        h1 {
            color: red;
        }

        .box {
            background-color: royalblue;
            width: 100px;
            height: 100px;
        }
    </style>
</head>

<body>
    <h1>Hello World</h1>
    <div class="box"></div>


    <script src="./jquery-3.6.0.js">
    </script>

    <script>

        //在這個標籤裡面才能執行
        //要用JQ之前，記得先引用，順序很重要

        $('h1').css('color', 'blue');
        $('.box').css('background-color', 'red');


    </script>
</body>

</html>