Run some code only after a script has been executed

test_script_execution.js

// createdObj is an object created by the script

// setup that should run after the script has been executed
var setup = function(){
  console.log('the script is on the page and did execute');
  console.log(typeof createdObj, 'does it exist?'); // -> function
};
 
// attach the script to the page
var script = document.createElement("script");
script.id = "test-snippet";
script.src = "https://test.api.com/test/snippet.js";
(document.getElementsByTagName('head')[0] || document.getElementsByTagName('body')[0] || document.getElementsByTagName('script')[0].parentNode).insertBefore(script, null);
 
console.log('the script is on the page but did not execute');
console.log(typeof createdObj, 'does it exist?'); // -> undefined
 
// Standard Check
script.onreadystatechange = function (){
// call setup when the script has beeen executed
 if (this.readyState == 'complete'){
   setup();
 }
}
// IE Check
script.onload = setup;