jankmeter_console.js

(function(){

/* scrolls the page to the bottom */
function s2b() {
	window.scrollTo(0,0); // reset screen position
	count = 0;
	sh = Math.max(document.documentElement.clientHeight, window.innerHeight || 0);
	h = Math.max(document.body.offsetHeight,document.body.scrollHeight) - sh;
	chunk = 100; // scrollwheel distance?
	if (h - chunk < 0) {
		throw 'Page too short';
		}
	fA=[];
	window.requestAnimationFrame(sl);
	ll=false;
}

/* scrolls the page by one scroll-wheel turn and gets framerate */
function sl() {
	if (!ll) {
		ll = performance.now();
		window.requestAnimationFrame(sl);
		return;
	}
	window.scrollBy(0,chunk);
	tl = performance.now();
	fA.push(parseInt(1000/(tl-ll)));
	ll = tl;
	count += chunk;
	if (count >= h) {
		window.scrollTo(0,0);
		cF(fA);
	} else {
		window.requestAnimationFrame(sl);
	}
}

/* calculate stats */
function cF(v) {
	// calculate median by sorting and select middle
	v.sort( function(a,b) {return a - b;} );
    var half = Math.floor(v.length/2);
    if(v.length % 2)
        var med = v[half];
    else
        var med = (v[half-1] + v[half]) / 2.0;
	
	// min and max from sorted array
	var mi = v[0];
	var ma = v[v.length-1];
	
	// mean by summing array and divide by total
	var to = 0;
	for (var i=0; i<v.length; i++) {
		to+=v[i];
	}
	var mn = parseInt(to/v.length);
	console.log("Median FPS: "+med);
	console.log("Mean FPS: "+mn);
	console.log("Min FPS: "+mi);
	console.log("Max FPS: "+ma);
}
s2b();
})();