Slide In

<script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/bundles/anime.umd.min.js"></script>
<script>
  (function () {
    // Slide In: the element slides in from fully off screen, from any edge,
    // and eases to a stop in its place.
    // Usage: <div data-slide-in>…</div>
    // It starts just past the edge of the nearest container that clips its
    // overflow (overflow: hidden or clip), or of the window if there is none.
    // Optional: data-from ("left", default, "right", "top" or "bottom"; give
    // several, like "left top right", and each loop uses the next),
    // data-distance (px to travel instead of from off screen), data-duration
    // (ms, default 900), data-delay (ms before the first entrance), data-loop
    // (hold, fade away and slide in again), data-hold (ms to stay when
    // looping, default 1400).
    var DEFAULTS = { from: 'left', duration: 900, delay: 0, hold: 1400 };

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

    // The box the element must leave to be "off screen".
    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 };
    }

    // Where to start: an x/y offset that puts the element just outside the box.
    function offset(el, from) {
      var d = +el.dataset.distance;
      var r = el.getBoundingClientRect();
      var c = clipBox(el);
      if (from === 'right') return { x: d || c.right - r.left + 8, y: 0 };
      if (from === 'top') return { x: 0, y: -(d || r.bottom - c.top + 8) };
      if (from === 'bottom') return { x: 0, y: d || c.bottom - r.top + 8 };
      return { x: -(d || r.right - c.left + 8), y: 0 };
    }

    function enter(el, from, done) {
      var o = offset(el, from);
      anime.utils.set(el, { x: o.x, y: o.y, opacity: 1 });
      anime.animate(el, {
        x: 0,
        y: 0,
        duration: +el.dataset.duration || DEFAULTS.duration,
        ease: 'out(4)',
        onComplete: done
      });
    }

    function cycle(el) {
      var d = el.dataset;
      var s = el._sli;
      var froms = (d.from || DEFAULTS.from).split(/[\s,]+/);
      enter(el, froms[s.n++ % froms.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._sli;
          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-slide-in]').forEach(function (el) {
        if (el._sli) return;
        el._sli = { 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="toast" data-slide-in>New message</div>

<!-- or from the right, sliding just 120px: -->
<div class="toast" data-slide-in data-from="right" data-distance="120">New message</div>