User Timing polyfill (http://www.w3.org/TR/user-timing/)

performance.js

/**
 * User Timing polyfill (http://www.w3.org/TR/user-timing/)
 * @author RubaXa <[email protected]>
 */
(function (window){
	var
		  startOffset = Date.now ? Date.now() : +(new Date)
		, performance = window.performance || {}

		, _entries = []
		, _marksIndex = {}

		, _filterEntries = function (key, value){
			var i = 0, n = _entries.length, result = [];
			for( ; i < n; i++ ){
				if( _entries[i][key] == value ){
					result.push(_entries[i]);
				}
			}
			return	result;
		}

		, _clearEntries = function (type, name){
			var i = _entries.length, entry;
			while( i-- ){
				entry = _entries[i];
				if( entry.entryType == type && (name === void 0 || entry.name == name) ){
					_entries.splice(i, 1);
				}
			}
		}
	;


	if( !performance.now ){
		performance.now = performance.webkitNow || performance.mozNow || performance.msNow || function (){
			return (Date.now ? Date.now() : +(new Date)) - startOffset;
		};
	}


	if( !performance.mark ){
		performance.mark = performance.webkitMark || function (name){
			var mark = {
				  name:			name
				, entryType:	'mark'
				, startTime:	performance.now()
				, duration:		0
			};
			_entries.push(mark);
			_marksIndex[name] = mark;
		};
	}


	if( !performance.measure ){
		performance.measure = performance.webkitMeasure || function (name, startMark, endMark){
			startMark	= _marksIndex[startMark].startTime;
			endMark		= _marksIndex[endMark].startTime;

			_entries.push({
				  name:			name
				, entryType:	'measure'
				, startTime:	startMark
				, duration:		endMark - startMark
			});
		};
	}


	if( !performance.getEntriesByType ){
		performance.getEntriesByType = performance.webkitGetEntriesByType || function (type){
			return _filterEntries('entryType', type);
		};
	}


	if( !performance.getEntriesByName ){
		performance.getEntriesByName = performance.webkitGetEntriesByName || function (name){
			return _filterEntries('name', name);
		};
	}


	if( !performance.clearMarks ){
		performance.clearMarks = performance.webkitClearMarks || function (name){
			_clearEntries('mark', name);
		};
	}


	if( !performance.clearMeasures ){
		performance.clearMeasures = performance.webkitClearMeasures || function (name){
			_clearEntries('measure', name);
		};
	}


	// exports
	window.performance = performance;

	if( typeof define === 'function' && (define.amd || define.ajs) ){
		define('performance', [], function (){ return performance });
	}
})(window);

performance.test.js

(function (){
	module('performance');

	function sleep(delay){
		var start = performance.now();
		while( true ){
			if( performance.now() - start >= delay ){
				break;
			}
		}
	}


	test('now', function (){
		var start = performance.now();
		sleep(1);
		ok(performance.now() - start < 1.5);
	});


	test('performance.mark', function (){
		performance.mark("foo");
		sleep(5);
		performance.mark("bar");
		sleep(10);
		performance.mark("baz");

		equal(performance.getEntriesByType('mark').length, 3);
		ok(performance.getEntriesByName('baz')[0].startTime - performance.getEntriesByName('bar')[0].startTime < 11, 'baz - bar');
		ok(performance.getEntriesByName('bar')[0].startTime - performance.getEntriesByName('foo')[0].startTime < 6, 'bar - foo');

		performance.clearMarks('bar');

		equal(performance.getEntriesByType('mark').length, 2);
		equal(performance.getEntriesByName('foo').length, 1);
		equal(performance.getEntriesByName('bar').length, 0);
		equal(performance.getEntriesByName('baz').length, 1);

		performance.clearMarks();
		equal(performance.getEntriesByType('mark').length, 0);
	});


	test('performance.measure', function (){
		performance.mark("foo");
		sleep(5);
		performance.mark("bar");

		performance.measure('foo_bar', 'foo', 'bar');

		equal(performance.getEntriesByType('measure').length, 1);
		ok(performance.getEntriesByName('foo_bar')[0].duration < 6, performance.getEntriesByName('foo_bar')[0].duration+'');

		performance.mark("foo");
		sleep(5);
		performance.mark("bar");
		sleep(5);
		performance.mark("foo");

		performance.measure('foo_bar', 'foo', 'bar');
		equal(performance.getEntriesByType('measure').length, 2);
		ok(performance.getEntriesByName('foo_bar')[1].duration < -5, performance.getEntriesByName('foo_bar')[1].duration+'');

		performance.clearMarks();
		performance.clearMeasures();
		equal(performance.getEntriesByType('measure').length, 0);
	});
})();

there are two issues with this implementation, related to lack of fail-safe logic in measureAPI:

1. according to W3 user-timing specs, startMark and endMark are optional. Thus, the polyfill should implement fail safe for such use case.
2. modern browsers support built-in/app-lifecycle marks to also be used as startMark and endMark in measure. This implementation assumes the above exists in internal cache (_marksIndex ), and access it without validating.

Не хватает timing и navigation http://www.w3.org/TR/navigation-timing/#sec-navigation-timing-interface