let time = 0;

function render(t) {
    console.log(t - time); //間隔約 16~17 毫秒，約 60 FPS，根據硬體
    time = t;
    // setTimeout(render, 1000 / 60); //如果要跑多次，這邊也要放一個 setTimeout
    requestAnimationFrame(render);
}

// setInterval(render, 1000 / 60); //60 FPS
// setTimeout(render, 1000 / 60); //如果 setTimeout 只放這裡，只會跑一次

requestAnimationFrame(render);