themes/base: xhr.js: clean code style, implement XHR.get() and XHR.poll() convenience functions

themes/base/htdocs/luci-static/resources/xhr.js

@@ -19,6 +19,9 @@ XHR = function()
 	}
 
 	this.busy = function() {
+		if (!this._xmlHttp)
+			return false;
+
 		switch (this._xmlHttp.readyState)
 		{
 			case 1:
@@ -161,3 +164,41 @@ XHR = function()
 		return obj;
 	}
 }
+
+XHR.get = function(url, data, callback)
+{
+	(new XHR()).get(url, data, callback);
+}
+
+XHR.poll = function(interval, url, data, callback)
+{
+	if (isNaN(interval) || interval <= 1)
+		interval = 5;
+
+	if (!XHR._q)
+	{
+		XHR._t = 0;
+		XHR._q = [ ];
+	}
+
+	XHR._q.push({
+		interval: interval,
+		callback: callback,
+		url:      url,
+		data:     data,
+		xhr:      new XHR()
+	});
+
+	if (!XHR._i)
+	{
+		XHR._i = window.setInterval(function() {
+			for (var i = 0, e = XHR._q[0]; i < XHR._q.length; e = XHR._q[++i])
+			{
+				if (!(XHR._t % e.interval) && !e.xhr.busy())
+					e.xhr.get(e.url, e.data, e.callback);
+			}
+
+			XHR._t++;
+		}, 1000);
+	}
+}