Javascript onload event - how to tell if script is already loaded?

Question

How can I use javascript to determine if an HTMLScriptElement has already been fully loaded?

How can I determine if a dynamically loaded script has finished loading without using the onload or onreadystate change events?

Code is as follows:

   TOOL.loadScript = function (url, callback, reappend, deepSearch) {
      var head, curr, child, tempScript, alreadyAppended, queue, 
      alreadyHandled, script, handler, loadFunc; 

      head = document.getElementsByTagName("head")[0];
      tempScript = document.createElement("script");
      tempScript.src = url;
      alreadyAppended = false;

      queue = []; 

      if (deepSearch) {
         // search entire document
         queue.push(document.firstElementChild);
      }
      else { 
         // just search the head element
         queue.push(head); 
      }

      while (queue.length !== 0) { 
         curr = queue.shift();

         // add child nodes to queue
         child = curr.firstElementChild; 
         if (child !== null && child !== undefined) { 
            queue.push(child);
            child = child.nextElementSibling;
            while (child !== null && child !== undefined) { 
               queue.push(child);
               child = child.nextElementSibling;
            } 
         }

         if (curr.tagName !== null && curr.tagName !== undefined) {
            if (curr.tagName.toLowerCase() === "script" && curr.src === tempScript.src) {
               script = curr;
               alreadyAppended = true;
               break;
            }
         }
      }

      if (!alreadyAppended) { 
         script = document.createElement("script");
         script.type = "text/javascript"; 
         script.async = true; 
         script.src = url; 
      } 

      alreadyHandled = false; 

      handler = function (event) {
         console.log("handling event..."); 
         if (!alreadyHandled) { 
            if ((!event.readyState) || (event && (event.readyState === "loaded" || event.readyState === "complete"))) {  
               alreadyHandled = true; 
               callback.apply(script, [url]);
               if (loadFunc) { 
                  loadFunc.apply(script, arguments); 
               }
            }
         }
      }; 

      if (script.onreadystatechange === undefined) { 
         loadFunc = script.onload;
         script.onload = handler; 
      } 
      else { 
         loadFunc = script.onreadystatechange; 
         script.onreadystatechange = handler; 
      } 

I need help here. I want the callback function to fire even if alreadyAppeneded === true and the same script was already loaded, but only if that script is completely finished loading.

      if (!alreadyAppended || (alreadyAppended && reappend)) { 
         head.appendChild(script); 
      } 
   };

BOTTOM LINE: How do I determine if a script has completed loading? Please ask me questions if needed.

Thank you.

Answer 1

Why not add an id to the script element? Check to see if the id exists before continuing....

function includeJs(jsFilePath) {

  if (document.getElementById(jsFilePath+"_script")) {
    return;
  }
  var js = document.createElement("script");

  js.type = "text/javascript";
  js.id = jsFilePath+"_script";
  js.src = jsFilePath;

  document.body.appendChild(js); 
}