js引入方式

<!DOCTYPE html>
<html lang="en">
<head>
   <meta charset="UTF-8">
   <meta name="viewport" content="width=device-width, initial-scale=1.0">
   <title>js引入方式</title>

   <!-- <script>
       alert("hello js");
   </script> -->

   <script src="js/demo.js"></script>
</head>
<body>
   
</body>
</html>