Script tag nuanses in JavaScript

Please note that in the script tag, you can either write code or include a file. Trying to do both at the same time won't work. So the following code doesn't work:

index.html<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title></title>
    <script src="script.js">
      alert('text');
    </script>
  </head>
  <body>
    
  </body>
</html>