gistfile1.js

var count = num = 1000;
var start = Date.now();

function proc(){
	if(!--count){
		console.log((Date.now() - start) / num);
		return;
	}
	
	defer();
}

var script = document.createElement('script');
script.src  = 'data:text/javascript,';
script.onload = function () {
	document.body.removeChild(script);
	
	proc();
}

function defer(){
	document.body.appendChild(script);
}

defer();