var stats = new Stats();
stats.showPanel( 1 ); // 0: fps, 1: ms, 2: mb, 3+: custom
document.body.appendChild( stats.dom );
function animate() {
	stats.begin();
	// monitored code goes here
	stats.end();
	requestAnimationFrame( animate );
}
requestAnimationFrame( animate );

javascript:(function(){var script=document.createElement('script');script.onload=function(){var stats=new Stats();document.body.appendChild(stats.dom);requestAnimationFrame(function loop(){stats.update();requestAnimationFrame(loop)});};script.src='https://mrdoob.github.io/stats.js/build/stats.min.js';document.head.appendChild(script);})()