Tracking In

<script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/bundles/anime.umd.min.js"></script>
<script>
  (function () {
    // Tracking In: text fades in from a soft blur while its letter spacing
    // tightens from wide to normal, drawing the letters together.
    // Usage: <h1 data-tracking-in>Breathe in</h1>
    // Optional: data-loop (spacing opens back out as the text fades, then
    // tightens again), data-hold (ms to stay before fading), data-spacing (how
    // wide it starts, in em; default 0.5), data-duration (ms), data-delay (ms
    // before starting).
    var DEFAULTS = { spacing: 0.5, duration: 1400, delay: 0, hold: 1800 };

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

    // The element's own letter spacing, in em, so it scales with the font.
    function baseSpacing(el) {
      var cs = getComputedStyle(el);
      var px = parseFloat(cs.letterSpacing) || 0;
      return px / parseFloat(cs.fontSize);
    }

    // True when the text sits on one line at rest. Then it's kept on one line
    // while the spacing is wide, instead of wrapping and jumping about.
    function fitsOneLine(el) {
      var h = el.offsetHeight;
      el.style.whiteSpace = 'nowrap';
      var one = el.offsetHeight === h;
      el.style.whiteSpace = '';
      return one;
    }

    function play(el) {
      var d = el.dataset;
      var loop = d.loop !== undefined && d.loop !== 'false';
      var duration = +d.duration || DEFAULTS.duration;
      var base = baseSpacing(el);
      var wide = base + (+d.spacing || DEFAULTS.spacing);
      var oneLine = fitsOneLine(el);
      // Letter spacing also adds space after the last letter, which pushes
      // centred text left. An equal indent on the left keeps it centred.
      var centred = oneLine && getComputedStyle(el).textAlign === 'center';

      if (oneLine) el.style.whiteSpace = 'nowrap';
      var into = {
        letterSpacing: [wide + 'em', base + 'em'],
        opacity: [0, 1],
        filter: ['blur(8px)', 'blur(0px)'],
        duration: duration,
        ease: 'outExpo'
      };
      if (centred) into.textIndent = [wide - base + 'em', '0em'];

      var tl = anime.createTimeline({
        loop: loop,
        loopDelay: 300,
        delay: +d.delay || DEFAULTS.delay,
        onComplete: function () {
          // Hand the spacing back to the stylesheet.
          ['letterSpacing', 'textIndent', 'filter', 'whiteSpace'].forEach(function (p) { el.style[p] = ''; });
        }
      });
      tl.add(el, into);
      if (loop) {
        var out = {
          letterSpacing: wide + 'em',
          opacity: 0,
          filter: 'blur(8px)',
          duration: duration * 0.6,
          ease: 'inQuad'
        };
        if (centred) out.textIndent = wide - base + 'em';
        tl.add(el, out, '+=' + (+d.hold || DEFAULTS.hold));
      }
    }

    function init() {
      var io = new IntersectionObserver(function (entries) {
        entries.forEach(function (e) {
          if (!e.isIntersecting) return;
          io.unobserve(e.target);
          play(e.target);
        });
      }, { threshold: 0.2 });
      document.querySelectorAll('[data-tracking-in]').forEach(function (el) {
        if (el._trk) return;
        el._trk = true;
        if (reduced()) return;
        el.style.opacity = 0;
        io.observe(el);
      });
    }

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

<h1 data-tracking-in>Breathe in</h1>

<!-- or, looping: -->
<h1 data-tracking-in data-loop>Breathe in</h1>