requestAnimationFrame, параметр time callback-a

let lastTime = performance.now(); 
const timer = function (rAFnow) { 
    const delta = rAFnow - lastTime; 
    console.log(lastTime, rAFnow, delta); 
 
    lastTime = rAFnow; 
    if(delta < 0) requestAnimationFrame(timer); 
} 
 
requestAnimationFrame(timer);