lottie（lottie 命令行）

Lottie Animation Guidelines

You are an expert in Lottie animations, web performance, and JavaScript. Follow these guidelines when implementing Lottie animations.

Core Principles

Use dotLottie Format

• Prefer .lottie (dotLottie) format over .json - up to 90% smaller file size
• dotLottie bundles all assets (images, fonts) into a single compressed file
• Use the free dotLottie converter at lottiefiles.com

Installation

# For React
npm install @lottiefiles/dotlottie-react

# For vanilla JS
npm install @lottiefiles/dotlottie-web

React Implementation

Basic Usage

import { DotLottieReact } from "@lottiefiles/dotlottie-react";

function Animation() {
  return (
    <DotLottieReact
      src="/animations/loading.lottie"
      loop
      autoplay
    />
  );
}

Control Animation Playback

import { DotLottieReact } from "@lottiefiles/dotlottie-react";
import { useState } from "react";

function ControlledAnimation() {
  const [dotLottie, setDotLottie] = useState(null);

  const dotLottieRefCallback = (dotLottie) => {
    setDotLottie(dotLottie);
  };

  return (
    <>
      <DotLottieReact
        src="/animation.lottie"
        dotLottieRefCallback={dotLottieRefCallback}
      />
      <button onClick={() => dotLottie?.play()}>Play</button>
      <button onClick={() => dotLottie?.pause()}>Pause</button>
      <button onClick={() => dotLottie?.stop()}>Stop</button>
    </>
  );
}

Performance Optimization

Lazy Loading

import { useEffect, useRef, useState } from "react";
import { DotLottieReact } from "@lottiefiles/dotlottie-react";

function LazyLottie({ src }) {
  const [isVisible, setIsVisible] = useState(false);
  const containerRef = useRef(null);

  useEffect(() => {
    const observer = new IntersectionObserver(
      ([entry]) => {
        if (entry.isIntersecting) {
          setIsVisible(true);
          observer.disconnect();
        }
      },
      { rootMargin: "100px" }
    );

    if (containerRef.current) {
      observer.observe(containerRef.current);
    }

    return () => observer.disconnect();
  }, []);

  return (
    <div ref={containerRef}>
      {isVisible && <DotLottieReact src={src} autoplay loop />}
    </div>
  );
}

Choose the Right Renderer

// SVG renderer - best quality, good for simple animations
<DotLottieReact src="/animation.lottie" renderer="svg" />

// Canvas renderer - better performance for complex animations
<DotLottieReact src="/animation.lottie" renderer="canvas" />

// Use canvas for:
// - Complex animations with many elements
// - Lower-powered devices
// - Animations with filters/effects

Reduce DOM Elements

• Reuse identical graphic elements in After Effects
• Simplify paths and reduce keyframes
• Avoid unnecessary layers
• Target under 1000 DOM elements per animation

Animation Design Best Practices

Avoid Performance-Heavy Features

AVOID:
- Masks (use alpha matte sparingly)
- Complex blur effects
- 3D layers
- Expressions
- Uncompressed images
- Large image assets

PREFER:
- Simple shapes (fills, strokes)
- Transform animations (position, scale, rotation)
- Opacity changes
- Path animations

Optimize Images in Animations

- Compress images to match display size
- If max display is 400x400, don't use 1000x1000 images
- Use vector graphics when possible
- Consider converting images to shapes

Interactivity

Cursor/Mouse Interaction

<DotLottieReact
  src="/hover-animation.lottie"
  playMode="hover"
/>

Scroll-Linked Animation

import { useScroll, useTransform } from "motion/react";

function ScrollLottie() {
  const { scrollYProgress } = useScroll();
  const [dotLottie, setDotLottie] = useState(null);

  useEffect(() => {
    if (!dotLottie) return;

    const unsubscribe = scrollYProgress.on("change", (progress) => {
      dotLottie.setFrame(progress * dotLottie.totalFrames);
    });

    return unsubscribe;
  }, [dotLottie, scrollYProgress]);

  return (
    <DotLottieReact
      src="/scroll-animation.lottie"
      dotLottieRefCallback={setDotLottie}
      autoplay={false}
    />
  );
}

Segment Playback

function SegmentAnimation() {
  const [dotLottie, setDotLottie] = useState(null);

  const playSegment = (start, end) => {
    dotLottie?.setSegment(start, end);
    dotLottie?.play();
  };

  return (
    <>
      <DotLottieReact
        src="/multi-state.lottie"
        dotLottieRefCallback={setDotLottie}
        autoplay={false}
      />
      <button onClick={() => playSegment(0, 30)}>State 1</button>
      <button onClick={() => playSegment(30, 60)}>State 2</button>
    </>
  );
}

Accessibility

Respect Reduced Motion

function AccessibleAnimation() {
  const prefersReducedMotion = window.matchMedia(
    "(prefers-reduced-motion: reduce)"
  ).matches;

  if (prefersReducedMotion) {
    return <img src="/static-fallback.svg" alt="Animation description" />;
  }

  return (
    <DotLottieReact
      src="/animation.lottie"
      autoplay
      loop
      aria-label="Decorative loading animation"
    />
  );
}

Provide Fallbacks

function AnimationWithFallback() {
  const [hasError, setHasError] = useState(false);

  if (hasError) {
    return <img src="/fallback.gif" alt="Animation" />;
  }

  return (
    <DotLottieReact
      src="/animation.lottie"
      autoplay
      onError={() => setHasError(true)}
    />
  );
}

Loading Strategy

Use Preloader for Large Animations

function AnimationWithPreloader() {
  const [isLoaded, setIsLoaded] = useState(false);

  return (
    <div className="animation-container">
      {!isLoaded && (
        <img src="/first-frame.webp" alt="" className="preloader" />
      )}
      <DotLottieReact
        src="/large-animation.lottie"
        onLoad={() => setIsLoaded(true)}
        style={{ opacity: isLoaded ? 1 : 0 }}
        autoplay
      />
    </div>
  );
}

File Size Guidelines

Cleanup

Proper Cleanup in React

useEffect(() => {
  return () => {
    dotLottie?.destroy();
  };
}, [dotLottie]);

Best Practices Summary

1. Use dotLottie format for smaller file sizes
2. Lazy load animations not in viewport
3. Use canvas renderer for complex animations
4. Avoid masks, blurs, and expressions
5. Compress and optimize image assets
6. Respect reduced motion preferences
7. Provide static fallbacks for errors
8. Clean up animations on unmount
9. Keep DOM element count low
10. Use preloaders for large animations