Simple example about creating embed code

embed-code.js

// index.html
// embed code
<script type="text/javascript" id="hs-script-loader" async defer src="//online-script.com/script-loader/XXXX.js"></script>

// online-script.com/script-loader/XXXX.js
(function (id, src) {
  if (document.getElementById(id)) { return; }
  var js = document.createElement('script');
  js.src = src;
  js.type = 'text/javascript';
  js.id = id;
  var e = document.getElementsByTagName('script')[0];
  e.parentNode.insertBefore(js, e);
})('my-script', '//online-script.com/script/YYYY.js');

// online-script.com/script/YYYY.js
// ... THE ENTIRE CODE GOES HERE ...