performanceprofiling.js

var performance = (function () {
	var my = {};
	
	// Wrap a function body in this to return a copy that instruments itself
	// If you want this to be useful, you should give your profiled function a name,
	// otherwise it will be identified as "", which is less than useful.
	my.profile = function (func) {
		return function () {
			var start = new Date().getTime(),
				time,
				retval = func.apply(this, Array.prototype.slice.call(arguments));
			
			time = new Date().getTime() - start;
			console.info("Call to function %o took %oms", func.name, time);
			
			return retval;
		};
	};
	
	// Use this to instrument chunks of code that are repeated frequently and tally the total
	// running time.
	// Ex: var profiler = performance.newProfiler("mycode");
	//     // some loop...
	//     profiler.begin("somesection");
	//     //... code
	//     profiler.end("somesection");
	//     // end loop
	//     profiler.report(true); // alerts total running time of the inner segment
	my.newProfiler = function (name) {
		var profiler = {},
			start = new Date().getTime(),
			profiles = {};
			
		function newProfile() {
			var profile = {},
				total = 0,
				last;
			
			profile.getTotal = function () {
				return total;
			};
			
			profile.start = function () {
				last = new Date().getTime();
			};
			
			profile.stop = function () {
				total += new Date().getTime() - last;
			};
			
			return profile;
		}
		
		profiler.begin = function (section) {
			if (!(section in profiles)) {
				profiles[section] = newProfile();
			}
			
			profiles[section].start();
		};
		
		profiler.end = function (section) {
			if (!section in profiles) {
				console.error("Profiler: profile %s not found", section);
			}
			
			profiles[section].stop();
		};
		
		profiler.report = function (useAlert) {
			var key,
				profile,
				total = 0,
				report = ["Results for profiler " + name + ":"],
				i,
				l;
			
			for (key in profiles) {
				profile = profiles[key];
				total += profile.getTotal();
				report.push("Section " + key + " " + profile.getTotal() + "ms");
			}
			
			report.push("Total: " + total + "ms");
			if (useAlert) {
				alert(report.join("\n"));
			} else {
				for (i = 0, l = report.length; i < l; i++) {
					console.info(report[i]);
				}
			}
		};
		
		return profiler;
	};
	
	return my;
}());