https://gbkgames.org/jsload/fpsCheck.js

1// fpsCheck.js
2
3document.addEventListener('DOMContentLoaded', function() {
4    var fps = document.getElementById('fps');
5    var startTime = Date.now();
6    var frame = 0;
7
8    function tick() {
9        var time = Date.now();
10        frame++;
11        if (time - startTime > 1000) {
12            fps.innerHTML = (frame / ((time - startTime) / 1000)).toFixed(1);
13            startTime = time;
14            frame = 0;
15        }
16        window.requestAnimationFrame(tick);
17    }
18    tick();
19
20    // Show FPS counter if enabled
21    if (localStorage.getItem('fpsCounterEnabled') === 'true') {
22        fps.style.display = 'block';
23    } else {
24        fps.style.display = 'none';
25    }
26});