Use Google Analytics (GA) events (https://developers.google.com/analytics/devguides/collection/gajs/eventTrackerGuide) to track & log JavaScript exceptions

send_exception_to_ga.js

Utility.send_exception_to_ga = function()
		{
			if(true || window.settings && window.settings.debug)
			{
				return;
			}
			var gOldOnError = window.onerror;
			window.onerror = function(message, url, line) {
				var e_obj = [
					  "_trackEvent"
					, "JS Exception Error"
					, message
					, (url + " (" + line + ")")
					, 0
					, true
				];
				if (typeof(_gaq) === "object") {
					_gaq.push(e_obj);
				}
				if (gOldOnError)
				{
					return gOldOnError(message, url, line);
				} else {
					console.log("Unhandled Exception");
					console.log(e_obj);
				}
				return false;
			};
		};