Waapi

Web Animations API for FrameVideo

When To Use

Use WAAPI for:

• Zero-dependency animations — no external libraries needed
• Lightweight DOM motion — simple transforms and opacity changes
• Native browser performance — browser-optimized keyframe engine
• Generated animations — creating animations from structured data
• Minimal bundle size — when every KB counts

Do NOT Use

Avoid WAAPI for:

• Complex timeline sequencing — use gsap (better timeline control)
• Default choice — use gsap unless you specifically want zero dependencies
• CSS-only decoration — use css-animations (simpler)
• 3D/WebGL — use three
• Designer exports — use lottie

Quick Start

Basic WAAPI animation in FrameVideo:

<div id="orb" class="clip orb" data-start="2" data-duration="3">Animate me</div>

<script>
  const orb = document.getElementById("orb");
  const animation = orb.animate(
    [
      { transform: "translateX(-160px) scale(0.8)", opacity: 0 },
      { transform: "translateX(0) scale(1)", opacity: 1, offset: 0.35 },
      { transform: "translateX(120px) scale(1.08)", opacity: 1 },
    ],
    {
      duration: 3000,
      delay: 2000,
      easing: "cubic-bezier(0.2, 0, 0, 1)",
      fill: "both",        // REQUIRED for FrameVideo
      iterations: 1,
    },
  );

  animation.pause();     // Pause immediately
</script>

Key points:

1. Use fill: "both" to hold seeked states
2. Call animation.pause() after creation
3. Use finite iterations

Contract

• Create animations synchronously during composition initialization.
• Use element.animate(...) with finite duration and iterations.
• Use fill: "both" so seeked states persist.
• Pause animations after creation or let the adapter pause them on first seek.
• Avoid callbacks and promises for render-critical state.

The adapter calls document.getAnimations(), sets each animation's currentTime to FrameVideo time in milliseconds, then pauses it.

Basic Pattern

<div id="orb" class="clip orb" data-start="2" data-duration="3" data-track-index="2"></div>

<script>
  const orb = document.getElementById("orb");
  const animation = orb.animate(
    [
      { transform: "translate3d(-160px, 0, 0) scale(0.8)", opacity: 0 },
      { transform: "translate3d(0, 0, 0) scale(1)", opacity: 1, offset: 0.35 },
      { transform: "translate3d(120px, 0, 0) scale(1.08)", opacity: 1 },
    ],
    {
      duration: 3000,
      delay: 2000,
      easing: "cubic-bezier(0.2, 0, 0, 1)",
      fill: "both",
      iterations: 1,
    },
  );

  animation.pause();
</script>

Stagger Pattern

document.querySelectorAll(".token").forEach((token, index) => {
  const animation = token.animate(
    [
      { transform: "translateY(24px)", opacity: 0 },
      { transform: "translateY(0)", opacity: 1 },
    ],
    {
      duration: 620,
      delay: index * 80,
      easing: "cubic-bezier(0.2, 0, 0, 1)",
      fill: "both",
      iterations: 1,
    },
  );
  animation.pause();
});

Good Uses

• Lightweight DOM motion where CSS keyframes are too rigid and GSAP is unnecessary.
• Generated animations from structured data.
• Simple timelines that can be represented as keyframes, delays, and offsets.

Avoid

• Infinite iterations.
• Depending on animation.finished to mutate render-critical DOM.
• Running separate clocks with requestAnimationFrame, timers, or performance.now().
• Animating layout properties when transforms and opacity can express the motion.
• Assuming clip-local start time is automatic. WAAPI adapter seeks document-level animation time; model clip offsets with delay or create the animation on an element whose visibility is controlled by FrameVideo timing.

Validation

After editing a WAAPI composition:

npx framevideo lint      # Check structure
npx framevideo validate  # Check runtime errors
npx framevideo preview   # Scrub timeline to verify seekability

Manual checks:

1. Fill mode — all animations use fill: "both"
2. Paused state — animations paused after creation
3. Finite iterations — no infinite loops
4. Seekability — scrub preview, animation holds at any frame
5. Performance — prefer transform/opacity over layout properties

Credits And References

• FrameVideo adapter source: packages/core/src/runtime/adapters/waapi.ts.
• MDN Web Animations API guide: https://developer.mozilla.org/docs/Web/API/Web_Animations_API/Using_the_Web_Animations_API
• MDN Animation.currentTime: https://developer.mozilla.org/en-US/docs/Web/API/Animation/currentTime