Bounce

The element crouches, jumps and stretches on the way up, then lands with a squash and a little second hop. It’s a cheerful way to say “look at me”.

How to use it

Paste the snippet just before </head>.
Add data-bounce to any element. It bounces once when it scrolls into view.
Add data-loop to keep bouncing every so often.

Options

Add any of these attributes to the same element.

`data-height`	How high it jumps, in px. Default 40.
`data-duration`	How long the whole bounce takes. Default 1100 ms.
`data-delay`	Wait before the first bounce. Default 0 ms.
`data-loop`	Bounce again every so often while it’s on screen.
`data-every`	Rest between bounces, when looping. Default 1600 ms.
`data-hover`	Also play it when the pointer moves over the element or it’s tapped.

Call animacious.bounce(el) to bounce it from your own code, for example when a new message arrives.

1 · Snippet

<script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/bundles/anime.umd.min.js"></script>
<script>
  (function () {
    // Bounce: the element crouches, jumps, stretches on the way up and lands
    // with a squash, then gives a little second hop before it settles.
    // Usage: <div data-bounce>…</div>
    // Optional: data-height (px it jumps, default 40), data-duration (ms for the
    // whole bounce, default 1100), data-delay (ms before the first bounce),
    // data-loop (bounce again every so often while in view), data-every (ms of
    // rest between loops, default 1600), data-hover (also bounce on hover or tap).
    // Script use: animacious.bounce(el) bounces it from code.
    var DEFAULTS = { height: 40, duration: 1100, delay: 0, every: 1600 };

    function on(v) { return v !== undefined && v !== 'false'; }
    function reduced() { return window.matchMedia('(prefers-reduced-motion: reduce)').matches; }

    function play(el, done) {
      var s = el._bnc;
      if (s.busy) { if (done) s.after = done; return; }
      if (reduced()) { if (done) done(); return; }
      s.busy = true;
      var d = el.dataset;
      var h = d.height === undefined ? DEFAULTS.height : +d.height;
      el.style.transformOrigin = '50% 100%'; // squash against the floor
      anime.animate(el, {
        keyframes: {
          '0%': { y: 0, scaleX: 1, scaleY: 1 },
          '10%': { y: 0, scaleX: 1.12, scaleY: 0.86, ease: 'out(2)' },          // crouch
          '20%': { scaleX: 0.92, scaleY: 1.1, ease: 'out(2)' },                 // stretch as it leaves
          '38%': { y: -h, scaleX: 1, scaleY: 1, ease: 'out(2)' },               // top of the jump
          '58%': { y: 0, scaleX: 0.95, scaleY: 1.06, ease: 'in(2)' },           // falling
          '65%': { scaleX: 1.18, scaleY: 0.8, ease: 'out(2)' },                 // land: squash
          '74%': { y: -h * 0.2, scaleX: 0.98, scaleY: 1.03, ease: 'out(2)' },   // little hop
          '86%': { y: 0, scaleX: 1.05, scaleY: 0.95, ease: 'in(2)' },
          '100%': { y: 0, scaleX: 1, scaleY: 1, ease: 'out(2)' }
        },
        duration: +d.duration || DEFAULTS.duration,
        onComplete: function () {
          s.busy = false;
          var after = s.after;
          s.after = null;
          if (done) done();
          if (after) after();
        }
      });
    }

    function cycle(el) {
      var s = el._bnc;
      play(el, function () {
        if (!on(el.dataset.loop)) return;
        clearTimeout(s.timer);
        s.timer = setTimeout(function () {
          if (s.visible) cycle(el);
          else s.waiting = true;
        }, +el.dataset.every || DEFAULTS.every);
      });
    }

    function init() {
      var io = new IntersectionObserver(function (entries) {
        entries.forEach(function (e) {
          var s = e.target._bnc;
          s.visible = e.isIntersecting;
          if (!e.isIntersecting) return;
          if (!s.started) {
            s.started = true;
            setTimeout(function () { cycle(e.target); }, +e.target.dataset.delay || DEFAULTS.delay);
          } else if (s.waiting) {
            s.waiting = false;
            cycle(e.target);
          }
        });
      }, { threshold: 0.2 });
      document.querySelectorAll('[data-bounce]').forEach(function (el) {
        if (el._bnc) return;
        el._bnc = {};
        if (on(el.dataset.hover)) {
          el.addEventListener('pointerenter', function () { play(el); });
          el.addEventListener('pointerdown', function () { play(el); });
        }
        if (!reduced()) io.observe(el);
      });
    }

    window.animacious = window.animacious || {};
    window.animacious.bounce = function (el) { if (el._bnc) play(el); };
    if (document.readyState === 'loading') document.addEventListener('DOMContentLoaded', init);
    else init();
  })();
</script>

2 · Your HTML

<span class="app-icon" data-bounce>…</span>

<!-- or bouncing every few seconds, higher: -->
<span class="app-icon" data-bounce data-loop data-height="60">…</span>