I made this method to load javascript functions dynamically. It does include the .js file but when I call a method, the method says that it is undefinited. The following to .js files are ajax_object.js and user_manager.js . The alert outside the function is read and works but the alert inside does not.

enter code here
//ajax_object.js
//Load a javascript library
 function loadJavascript( src, url ){

XMLHttpRequestObject=getXmlHttpRequestObject();

if( XMLHttpRequestObject){

    XMLHttpRequestObject.onreadystatechange = function()
    {
        if (XMLHttpRequestObject.readyState == 4 ){


            if (XMLHttpRequestObject.status == 200 || XMLHttpRequestObject.status == 304) {
                includeJavaScript( src, url, XMLHttpRequestObject.responseText );
            }
        }
    }

}

XMLHttpRequestObject.open('GET', url, true);
XMLHttpRequestObject.send(null);

  }//end LoadJavaScript

 //Add Library to header
function includeJavaScript(src, fileUrl, xmlObject)  { 
if ( ( xmlObject != null ) && ( !document.getElementById( src ) ) ){ 
    var documentHead = document.getElementsByTagName('HEAD').item(0);
    var includeScript = document.createElement( "script" );
    includeScript.language = "javascript";
    includeScript.type = "text/javascript";
    //includeScript.id = src;
    includeScript.src=fileUrl.concat(src);
    includeScript.defer = true;
    includeScript.text = xmlObject;
    documentHead.appendChild( includeScript );
} 
  } 

//user_manager.js
 //First alert is read
 alert("Outside User Manager");
  function selectUserManagerModuleType(){
XMLHttpRequestObject=getXmlHttpRequestObject();
//This doesn't work
    //throws selectUserManagerModuleType undefined
alert("Inside The User Manager");



    }