// SimpleComet v1.0 by Mandor // For more info, see http://www.mandor.net/2008/12/23/12 var comet = { // Determines the proper technique based on browser type. technique: /(Firefox|Safari)/i.test(navigator.userAgent) ? 1 : /MSIE/i.test(navigator.userAgent) ? 2 : 3, // Binds the proper transport to a specified stream. open: function(URL, push, disconnected) { this.push = push || new Function; this.disconnected = disconnected || new Function; this.URL = URL; this.active = true; switch (this.technique) { case 1: // We're doing XHR streaming! if (!this.transport) { this.transport = new XMLHttpRequest(); } this.eventID = 0; this.transport.open('GET', this.URL, true); this.transport.onreadystatechange = this.scope(this.XHRcallback, this); this.transport.send(null); break; case 2: // We're using a forever frame with that fancy IE hack. if (!this.transport) { this.transport = new ActiveXObject('htmlfile'); } this.transport.open(); this.transport.write(''); this.transport.close(); this.transport.parentWindow.push = this.push; this.transport.body.innerHTML = ''; setTimeout(this.scope(this.checkFrame, this), 500); break; case 3: // Falling back on using a standard forever frame. if (!this.transport) { this.transport = document.createElement('iframe'); } this.transport.style.display = 'none'; this.transport.src = this.URL; this.transport.onload = this.scope(this.close, this); document.body.appendChild(this.transport); break; } }, // Unbinds the transport. close: function() { if (!this.active) { return; } else { this.active = false; } switch (this.technique) { case 1: if (this.transport.readyState != 4) { this.transport.abort(); } break; case 2: this.transport.body.removeChild(this.transport.getElementById('SimpleComet')); break; case 3: this.transport.src = 'about:blank'; document.body.removeChild(this.transport); break; } this.disconnected(); }, // If the transport is incremental XHR (technique 1), we need to fetch _NEW_ events from the stream. XHRcallback: function() { if (this.transport.readyState == 4) { this.close(); return; } var events = this.transport.responseText.match(/(.+?)<\/comet>/g); while (events && events[this.eventID]) { this.push(events[this.eventID].substring(7, events[this.eventID].length-8)); this.eventID++; } }, // If the transport is an IE forever frame (technique 2), we need to check periodically if it's still alive. checkFrame: function() { if (!this.transport.getElementById('SimpleComet')) { return; } if (this.transport.getElementById('SimpleComet').readyState == 'complete') { this.close(); return; } setTimeout(this.scope(this.checkFrame, this), 500); }, // Used to change the scope of callback functions. scope: function(f, scope) { return function() { return f.apply(scope); } } }