Swing Drop In

The element drops down as if hung on a string, then swings like a pendulum from a point above it, each swing smaller, until it hangs at rest. A looping demo swings the other way first each time.

Open

How to use it

Paste the snippet just before </head>.
Add data-swing-drop-in to any element.
Set data-string to how far above it the string is tied, if you draw one.

Options

Add any of these attributes to the same element.

`data-angle`	How far it swings at first, in degrees. Default 24.
`data-string`	How far above the element’s top it hangs from, in px. A longer string makes a wider swing. Default 120.
`data-height`	Drop this many px instead of from just above the top of its container.
`data-duration`	How long the drop and swings take. Default 1800 ms.
`data-delay`	Wait before the first entrance. Default 0 ms.
`data-loop`	Hold, fade away and drop in again.
`data-hold`	How long it stays before fading, when looping. Default 1400 ms.

It drops from just above the top of the nearest container that clips its overflow (overflow: hidden or clip), or of the window. It swings round a point above itself, so the script sets transform-origin on the element.

1 · Snippet

<script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/bundles/anime.umd.min.js"></script>
<script>
  (function () {
    // Swing Drop In: the element drops down as if hung on a string, then
    // swings like a pendulum from a point above it, each swing smaller,
    // until it hangs at rest.
    // Usage: <div data-swing-drop-in>…</div>
    // It drops from just above the top of the nearest container that clips
    // its overflow (overflow: hidden or clip), or of the window. The script
    // sets transform-origin on the element (the point it hangs from).
    // Optional: data-angle (how far it swings at first, in degrees, default
    // 24), data-string (how far above the element it hangs from, in px,
    // default 120), data-height (px to drop instead), data-duration (ms,
    // default 1800), data-delay (ms before the first entrance), data-loop
    // (hold, fade away and drop in again; each loop swings the other way
    // first), data-hold (ms to stay when looping, default 1400).
    var DEFAULTS = { angle: 24, string: 120, duration: 1800, delay: 0, hold: 1400 };

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

    // The box the element drops into.
    function clipBox(el) {
      for (var p = el.parentElement; p && p !== document.body; p = p.parentElement) {
        var s = getComputedStyle(p);
        if (s.overflowX !== 'visible' || s.overflowY !== 'visible') return p.getBoundingClientRect();
      }
      return { left: 0, top: 0, right: window.innerWidth, bottom: window.innerHeight };
    }

    function enter(el, dir, done) {
      var d = el.dataset;
      var t = +d.duration || DEFAULTS.duration;
      var a = (d.angle === undefined ? DEFAULTS.angle : +d.angle || 0) * dir;
      var len = d.string === undefined ? DEFAULTS.string : +d.string || 0;
      anime.utils.set(el, { y: 0, rotate: 0 });
      var h = +d.height || el.getBoundingClientRect().bottom - clipBox(el).top + 8;
      // Hang from a point above the element's top centre.
      el.style.transformOrigin = '50% ' + -len + 'px';
      anime.utils.set(el, { y: -h, rotate: a * 0.5, opacity: 1 });
      anime.createTimeline({ onComplete: done })
        // Drop until the string pulls tight, with a little give at the end.
        .add(el, {
          y: [
            { to: 6, duration: t * 0.22, ease: 'in(2)' },
            { to: 0, duration: t * 0.1, ease: 'out(2)' }
          ]
        }, 0)
        // Swing back and forth, each swing smaller, and come to rest.
        .add(el, {
          rotate: [
            { to: a, duration: t * 0.2, ease: 'out(2)' },
            { to: -a * 0.62, duration: t * 0.18, ease: 'inOut(2)' },
            { to: a * 0.36, duration: t * 0.16, ease: 'inOut(2)' },
            { to: -a * 0.18, duration: t * 0.15, ease: 'inOut(2)' },
            { to: a * 0.07, duration: t * 0.14, ease: 'inOut(2)' },
            { to: 0, duration: t * 0.17, ease: 'out(2)' }
          ]
        }, 0);
    }

    function cycle(el) {
      var d = el.dataset;
      var s = el._sdi;
      enter(el, s.n++ % 2 ? -1 : 1, 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._sdi;
          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-swing-drop-in]').forEach(function (el) {
        if (el._sdi) return;
        el._sdi = { 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>

2 · Your HTML

<div class="sign" data-swing-drop-in>Open</div>

<!-- or a gentler swing from a shorter string: -->
<div class="sign" data-swing-drop-in data-angle="12" data-string="60">Open</div>