raf_example.js

// print 10 x's per second
function printXs(totalMs) {
  let begin = null;
  let printed = 0;
  function callback(tick) {
    // note begin time
    if (begin === null) {
      begin = tick;
    }
 
    // make sure we're still in the animation interval
    let lapsed = tick - begin;
    if (lapsed <= totalMs) {
      // calculate the number of x's to print now and print them
      let xs = "x".repeat(Math.floor(lapsed / 100) - printed);
      if (xs.length > 0) {
        printed += xs.length;
        console.log(xs);
      }
      // recur
      requestAnimationFrame(callback);
    }
    // print any remaining after our period has expired
    else if (printed < Math.floor(totalMs / 100)) {
      let xs = "x".repeat(Math.floor(totalMs / 100) - printed);
      console.log(xs);
    }
  }
  requestAnimationFrame(callback);
}