alsotang/frame_rate.html

## frame_rate.html
<body>
  <script>
    // record every requestAnimationFrame interval and use them to calculate the average framerate.
    let frameRate = 0;
    let historyInterval = [];
    let historyIntervalLength = 200;

    let lastTime = Date.now();

    requestAnimationFrame(function loop() {
      let now = Date.now();
      let interval = now - lastTime;
      lastTime = now;

      historyInterval.push(interval);
      if (historyInterval.length > historyIntervalLength) {
        historyInterval.shift();
      }

      frameRate = Math.round(1000 / (historyInterval.reduce((a, b) => a + b) / historyInterval.length));

      requestAnimationFrame(loop);
      console.log(`frameRate`, frameRate)
    });
  </script>
</body>
	<body>
	<script>
	// record every requestAnimationFrame interval and use them to calculate the average framerate.
	let frameRate = 0;
	let historyInterval = [];
	let historyIntervalLength = 200;

	let lastTime = Date.now();

	requestAnimationFrame(function loop() {
	let now = Date.now();
	let interval = now - lastTime;
	lastTime = now;

	historyInterval.push(interval);
	if (historyInterval.length > historyIntervalLength) {
	historyInterval.shift();
	}

	frameRate = Math.round(1000 / (historyInterval.reduce((a, b) => a + b) / historyInterval.length));

	requestAnimationFrame(loop);
	console.log(`frameRate`, frameRate)
	});
	</script>
	</body>