How to make javascript wait until it gets a valid response from synchronous http request? -


i know not idea use synchronous requests case need it.

i have tried make getenddate function calling if response lenght less 20 after first unsuccessfull request (if url gives short response) goes alert(enddate.eddayow); , getting error, , getenddate continues sending request every 500 ms.

i need getenddate function continue sending request until valid response , return valid object, , after continue next line of js. how achieve that?

var url = 'http://local.com/cgi-bin/hello2.pl'; // url returns plain text: // 1234567890 2013 05 may friday 13 23 45 01   var enddate = getenddate(url);  alert(enddate.eddayow);  function getenddate(url) {     var xmlhttp = getxmlhttp();     xmlhttp.open('get', url, false);     xmlhttp.send();     if (xmlhttp.status == 200 && xmlhttp.responsetext.length > 20) {         var n = xmlhttp.responsetext.split(" ");         return {             'edseconds': n[0],             'edyear': n[1],             'edmon': n[2],             'edmonname': n[3],             'eddayow': n[4],             'edday': n[5],             'edhour': n[6],             'edmin': n[7],             'edsec': n[8]         };     } else {         settimeout("getenddate(" + url + ")", 500);     } }   function getxmlhttp() {     var xmlhttp;     try {         xmlhttp = new activexobject("msxml2.xmlhttp");     } catch (e) {         try {             xmlhttp = new activexobject("microsoft.xmlhttp");         } catch (e) {             xmlhttp = false;         }     }     if (!xmlhttp && typeof xmlhttprequest != 'undefined') {         xmlhttp = new xmlhttprequest();     }     return xmlhttp; }

i don't know if satisfies requirement, rewrite this:

var enddate;  getenddate(url);  function do_rest(returndate) {     enddate = returndate;     alert(enddate.eddayow);      // more if need };   function getenddate(url) {     var xmlhttp = getxmlhttp();      xmlhttp.onreadystatechange = function() {         if (xmlhttp.readystate == 4) {             if (xmlhttp.status == 200 && xmlhttp.responsetext.length > 20) {                 var n = xmlhttp.responsetext.split(" ");                 do_rest({                     'edseconds': n[0],                     'edyear': n[1],                     'edmon': n[2],                     'edmonname': n[3],                     'eddayow': n[4],                     'edday': n[5],                     'edhour': n[6],                     'edmin': n[7],                     'edsec': n[8]                 });             } else {                 settimeout("getenddate(" + url + ")", 500);             }         }     }       xmlhttp.open('get', url, false);     xmlhttp.send(); }

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