Script to call external javascript file

demo.js

https://varvy.com/pagespeed/defer-loading-javascript.html

<script type="text/javascript">
function downloadJSAtOnload() {
var element = document.createElement("script");
element.src = "defer.js";
document.body.appendChild(element);
}
if (window.addEventListener)
window.addEventListener("load", downloadJSAtOnload, false);
else if (window.attachEvent)
window.attachEvent("onload", downloadJSAtOnload);
else window.onload = downloadJSAtOnload;
</script>


Specific instructions

1. Copy above code.

2. Paste code in your HTML just before the </body> tag (near the bottom of your HTML file).

3. Change the "defer.js" to the name of your external JS file.

4. Ensure the path to your file is correct. Example: if you just put "defer.js", then the file "defer.js" must be in the same folder as your HTML file. 


p.s. JS should be split into two groups:  one that the page needs to load and another that can be fully deferred