適当にベンチするやつ

bench.js

//bench.js

var bench = function(a){
	a.benches.forEach(function(e){
		console.time(e.name);
		for(var i = 0; i < a.count; i++){
			e.func();
		}
		console.timeEnd(e.name);
	});
};

//usage

bench({
	'count': 1000000, 
	'benches': [
		{
			'name': 'use with', 
			'func': function(){
				with(Math){
					var r = random();
				}
			}
		}, {
			'name': 'no use with', 
			'func': function(){
				var r = Math.random();
			}
		}
	]
});

/*
Output: 

use with: 235ms
no use with: 6ms

*/