Speed test: Components.utils.import() vs check + Components.utils.import()

importTest.js

var c = 30e3;

var tmr = "performance" in window && "now" in performance
	? performance
	: Date;
var Cu = Components.utils;

var i = c + 1, t = tmr.now();
while(--i)
	Cu.import("resource://gre/modules/Services.jsm");
var dt1 = tmr.now() - t;

var i = c + 1, t = tmr.now();
while(--i)
	if(!("Services" in window))
		Cu.import("resource://gre/modules/Services.jsm");
var dt2 = tmr.now() - t;

alert("import: " + dt1 + "\nimport with check: " + dt2 + ", speed up: " + dt1/dt2);
/*
Firefox 20.0.1:
import: 513.3255428895354
import with check: 71.60421052761376, speed up: 7.168929579798584
*/