javascript - How to make it work with Asynchronous -

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i want able results asynchronous method. reason works in other method. trying return response of callback method. can

ajax.getresults();  

instead of:

ajax.getresults(function(response){     // code here... }); 

here code...

function ajax(method, destination, sendtype){     this.method=method;     this.destination=destination;     this.sendtype=sendtype;     // creates xmlhttp object     this.create=function(){         var xmlhttp;         if(window.xmlhttprequest){             xmlhttp=new xmlhttprequest();         }else{             xmlhttp=new activexobject("microsoft.xmlhttp");         }         return xmlhttp;     }     this.request=function(callback){         var xmlhttp=this.create();         xmlhttp.onreadystatechange=function(){             if(xmlhttp.readystate==4 && xmlhttp.status==200){                 // response                 callback(xmlhttp.responsetext);             }         }         xmlhttp.open(this.method, this.destination, this.sendtype);         xmlhttp.send();     } }  // trying results this.request() ajax.prototype.getresults=function(){     var result;     this.request(function(response){         result=response;     });     return result; }  function ajaxtest(){     var ajax=new ajax('post', 'echo.php', true);     alert(ajax.getresults()); }