https://shimtimultimedia.com/assets/scripts/pages/contact-lightning.js

1'use strict';
2
3(() => {
4  const flashLayer = document.querySelector('[data-contact-lightning]');
5  if (!flashLayer) return;
6  const reducedMotion = window.matchMedia('(prefers-reduced-motion: reduce)');
7
8  let timeout = 0;
9  let animation = null;
10  let seed = 0x5b19a4d3;
11
12  const random = () => {
13    seed = (Math.imul(seed, 1664525) + 1013904223) >>> 0;
14    return seed / 4294967296;
15  };
16
17  const schedule = () => {
18    window.clearTimeout(timeout);
19    if (document.hidden || (reducedMotion.matches || document.documentElement.dataset.motion === 'reduce')) return;
20    timeout = window.setTimeout(runFlash, 6000 + random() * 14000);
21  };
22
23  const runFlash = () => {
24    if (document.hidden || (reducedMotion.matches || document.documentElement.dataset.motion === 'reduce')) {
25      schedule();
26      return;
27    }
28
29    const doubleFlash = random() > 0.58;
30    const strength = 0.065 + random() * 0.055;
31    const keyframes = doubleFlash
32      ? [
33          { opacity: 0, offset: 0 },
34          { opacity: strength * 0.72, offset: 0.1 },
35          { opacity: strength * 0.08, offset: 0.25 },
36          { opacity: strength, offset: 0.46 },
37          { opacity: strength * 0.14, offset: 0.67 },
38          { opacity: 0, offset: 1 },
39        ]
40      : [
41          { opacity: 0, offset: 0 },
42          { opacity: strength, offset: 0.18 },
43          { opacity: strength * 0.2, offset: 0.48 },
44          { opacity: 0, offset: 1 },
45        ];
46
47    animation?.cancel();
48    animation = flashLayer.animate(keyframes, {
49      duration: doubleFlash ? 760 + random() * 420 : 520 + random() * 360,
50      easing: 'linear',
51      fill: 'none',
52    });
53    animation.addEventListener('finish', schedule, { once: true });
54    animation.addEventListener('cancel', schedule, { once: true });
55  };
56
57  const reset = () => {
58    window.clearTimeout(timeout);
59    animation?.cancel();
60    animation = null;
61    flashLayer.style.opacity = '0';
62    schedule();
63  };
64
65  document.addEventListener('visibilitychange', reset);
66  reducedMotion.addEventListener('change', reset);
67  window.addEventListener('site-motion-change', reset);
68  schedule();
69})();