async-fns.js

const animationFrame = () => new Promise(window.requestAnimationFrame);

const load = (el=window) => new Promise(resolve => el.onload = resolve);

const timeout = (time) => new Promise(resolve => setTimeout(resolve, time))

loop.js

// https://coderwall.com/p/iygcpa/gameloop-the-correct-way

const animationFrame = () => new Promise(requestAnimationFrame);


const loop = async (draw=function(){}) => {
    let lastTimestamp = 0;
    let playing = true;
    setTimeout(() => playing = false, 20);

    while (playing) {
        let timestamp = await animationFrame();
        let delta = lastTimestamp ? timestamp - lastTimestamp : 0;
        draw({ delta, timestamp });
        lastTimestamp = timestamp;
    }
}

let count = 0;
loop(({ delta, timestamp }) => {
    console.log('delta', delta);
    console.log('ts', timestamp);
    console.log('count', count++);
});