Answers for "how to link a js fie"

linking a script .js

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