Answers for "implement js in another html page"

include script in html

<script type="text/javascript" src="/path/to/script.js"></script>

how to enter javascript in html

<script type="text/javascript">
  alert("This alert box was called with the onload event");
</script>

How to add js file to a site through url

var jsFile = document.createElement("script");
jsFile.src = "homePage.js";  // it can be path also  "{themes('/scripts/homePage.js')}"
document.body.appendChild(jsFile);  //append it as src to body