function GetHttpRequest() 
{ 
if ( window.XMLHttpRequest ) // Gecko
return new XMLHttpRequest() ;
else if ( window.ActiveXObject ) // IE
return new ActiveXObject("MsXml2.XmlHttp") ;
} 
function AjaxJS(sId, url){ 
 var oXmlHttp = GetHttpRequest() ;
 oXmlHttp.OnReadyStateChange = function() 
 { 
 
 if ( oXmlHttp.readyState == 4 ) 
 { 
 if ( oXmlHttp.status == 200 || oXmlHttp.status == 304 ) 
 {
 IncludeJS( sId, url, oXmlHttp.responseText );
 } 
 else 
 { 
 alert( 'XML request error: ' + oXmlHttp.statusText + ' (' + oXmlHttp.status + ')' ) ;
 } 
 } 
 } 
 oXmlHttp.open('GET', url, true);
 oXmlHttp.send(null);
 } 
 function IncludeJS(sId, fileUrl, source) 
 { 
 if ( ( source != null ) && ( !document.getElementById( sId ) ) ){ 
 var oHead = document.getElementsByTagName('HEAD').item(0);
 var oScript = document.createElement( "script" );
 oScript.language = "javascript";
 oScript.type = "text/javascript";
 oScript.id = sId;
 oScript.defer = true;
 oScript.text = source;
 oHead.appendChild( oScript );
 } 
 } 
//////////////// other method  ///////
function loadScript(url, callback){

    var script = document.createElement("script")
    script.type = "text/javascript";

    if (script.readyState){  //IE
        script.onreadystatechange = function(){
            if (script.readyState == "loaded" ||
                    script.readyState == "complete"){
                script.onreadystatechange = null;
                callback();
            }
        };
    } else {  //Others
        script.onload = function(){
            callback();
        };
    }

    script.src = url;
    document.getElementsByTagName("head")[0].appendChild(script);
}