var timer; // Place timer in global scope to avoid it getting GC'ed prematurely function handleRequest(request, response) { response.setHeader("Cache-Control", "no-cache", false); response.setHeader("Content-Type", "application/xml", false); response.write("<"); response.bodyOutputStream.flush(); response.processAsync(); timer = Components.classes["@mozilla.org/timer;1"] .createInstance(Components.interfaces.nsITimer); timer.initWithCallback(function() { response.write("?xml version='1.0'?>\u00D0\u00B6\n"); response.finish(); }, 10, Components.interfaces.nsITimer.TYPE_ONE_SHOT); }