javascript - Calling a XMLHttpRequest continuously -


at moment calling function on setinterval basis.

this function makes xmlhttprequest server update info. if there update available update image (using canvas element).

is optimum way sort of thing?

my code:

calling code:

    function startfeedup() {         if (tmrstartfeedup) window.clearinterval(tmrstartfeedup);         tmrstartfeedup = setinterval(getnextimage, 330);     }

my called function:

  var isprocess = false;    function getnextimage() {         try {             if (!isprocess) {                 isprocess = true;                 var urlts = '/cloud/isnewframes.ashx?alias=' + alias + '&version=' + version + '&guidlogon=' + guidlogon;                 var xmlhttp = new xmlhttprequest();                 xmlhttp.open("get", urlts, true);                                   xmlhttp.timeout = 200;                 xmlhttp.send();                 var nextts = xmlhttp.responsetext;              }                  isprocess = false;              }          catch (err) {             isprocess = false;             document.getelementbyid("divmode2").innerhtml = err;         }      }

other repeating xhr call, can use html5 web sockets allows maintain connection server, whereby server push data , when needed. web sockets relatively new , aren't supported old browsers.

your xhr asyncronous should listening on onreadystatechange event instead of expecting response available directly after send() call:

xmlhttp.open("get", urlts, true);                   xmlhttp.timeout = 200; xmlhttp.onreadystatechange = function(){     if(xmlhttp.readystate == 4 && xmlhttp.status == 200){         console.log("received " + xmlhttp.responsetext);     } } xmlhttp.send();

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