add external script in html code example
Example 1: script src tag in html
<script type="text/javascript"
src="file.js">
</script>
Example 2: how to link javascript to html
<script src="PathToYourFile.js"> </script>
<script type="text/javascript"
src="file.js">
</script>
<script src="PathToYourFile.js"> </script>