reference js file in html file code example
Example 1: how to link your js file to html
<script src="index.js"></script>
Example 2: how to link js to html
<script src="Your-JavaScript-File.js"></script> <!--If JS file is in same folder with HTML file-->
Example 3: include js in html
<html>
<head>
</head>
<body>
<script type="text/javascript" src=es4.js></script>
</body>
</html>