You can include not only single,
but also multiple files using several
script
tags:
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<script src="script1.js"></script>
<script src="script2.js"></script>
</head>
<body>
</body>
</html>
Make three scripts files. Include them in your HTML file. Check out their work.