var e = document.createElement('script');
e.type = 'text/javascript';
e.src = 'my_script_url';
e.error = e.onload = e.readystatechange = function(){
  if(!e.loaded && (!e.readyState || e.readyState == 'loaded' || e.readyState == 'complete')){
    e.loaded = 1;
    e.onerror = e.onload = e.onreadystatechange = null;
    e.parentNode.removeChild(e);
  }
};
  
var head = document.getElementByTagName('head');
if(head.length) head = head[0];
head.appendChild(e);