Split Open In

<script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/bundles/anime.umd.min.js"></script>
<script>
  (function () {
    // Split Open In: the element opens from its centre line outwards, like a
    // pair of curtains drawn apart, while its contents ease back to size.
    // Usage: <div data-split-open-in>…</div>
    // Optional: data-axis ("x", default, a vertical centre line that opens
    // to the sides; "y" a horizontal one that opens up and down; give both,
    // "x y", and each loop uses the next), data-duration (ms, default 900),
    // data-delay (ms before the first entrance), data-loop (hold, fade away
    // and open again), data-hold (ms to stay when looping, default 1400).
    var DEFAULTS = { axis: 'x', duration: 900, delay: 0, hold: 1400 };
    var PAD = 40;   // room past the edges, so a box-shadow isn't cut off

    function reduced() {
      return window.matchMedia('(prefers-reduced-motion: reduce)').matches;
    }

    function inset(v, h) {
      return 'inset(' + v + 'px ' + h + 'px ' + v + 'px ' + h + 'px)';
    }

    function enter(el, axis, done) {
      var d = el.dataset;
      var t = +d.duration || DEFAULTS.duration;
      // Clip to a line at the centre, then widen the clip to the full box.
      var start = axis === 'y'
        ? inset(el.offsetHeight / 2, -PAD)
        : inset(-PAD, el.offsetWidth / 2);
      // (from/to given together: the browser shortens a computed inset() to fewer values.)
      el.style.clipPath = start;
      anime.utils.set(el, { scale: 1.06, opacity: 1 });
      anime.animate(el, {
        clipPath: { from: start, to: inset(-PAD, -PAD), duration: t, ease: 'inOut(3)' },
        scale: { to: 1, duration: t * 1.1, ease: 'out(3)' },
        onComplete: function () {
          el.style.clipPath = '';
          done();
        }
      });
    }

    function cycle(el) {
      var d = el.dataset;
      var s = el._spo;
      var axes = (d.axis || DEFAULTS.axis).split(/[\s,]+/);
      enter(el, axes[s.n++ % axes.length], function () {
        if (d.loop === undefined || d.loop === 'false') return;
        setTimeout(function () {
          anime.animate(el, {
            opacity: 0,
            duration: 400,
            ease: 'out(2)',
            onComplete: function () {
              // Wait until it's back on screen before the next entrance.
              setTimeout(function () {
                if (s.visible) cycle(el);
                else s.waiting = true;
              }, 500);
            }
          });
        }, +d.hold || DEFAULTS.hold);
      });
    }

    function init() {
      var io = new IntersectionObserver(function (entries) {
        entries.forEach(function (e) {
          var s = e.target._spo;
          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-split-open-in]').forEach(function (el) {
        if (el._spo) return;
        el._spo = { n: 0 };
        if (reduced()) return;
        anime.utils.set(el, { opacity: 0 });
        io.observe(el);
      });
    }

    if (document.readyState === 'loading') document.addEventListener('DOMContentLoaded', init);
    else init();
  })();
</script>

<div class="card" data-split-open-in>Now showing</div>

<!-- or opening up and down: -->
<div class="card" data-split-open-in data-axis="y">Now showing</div>