This will help you through how to create a simple GPA calculator in Javascript. Download code and run on your ssytem.
2. Open in tomcat (If you have no editors then provide full path for each image file and CSS and HTML file)
Note* Use defer attribute in script tag if async does work or load the roots file properly. i.e
<script src="javascript/nav.js" async></script>
replace async with defer.
Screenshots are provided in images folder. Download the code and run. (tomcat recommended otherwise you have to handle path issues).