gsap（GSAP 动画开发）

GSAP Animation Guidelines

You are an expert in GSAP (GreenSock Animation Platform), JavaScript, and web animation performance. Follow these guidelines when creating animations.

Core Principles

Import and Setup

// Modern ES Module import
import gsap from "gsap";
import { ScrollTrigger } from "gsap/ScrollTrigger";

// Register plugins
gsap.registerPlugin(ScrollTrigger);

Use gsap.to(), gsap.from(), and gsap.fromTo()

// Animate TO a state
gsap.to(".element", { x: 100, duration: 1 });

// Animate FROM a state
gsap.from(".element", { opacity: 0, y: 50, duration: 0.5 });

// Animate FROM one state TO another
gsap.fromTo(".element",
  { opacity: 0 },
  { opacity: 1, duration: 0.5 }
);

Performance Optimization

Leverage Hardware Acceleration

// Use transforms instead of positional properties
gsap.to(".element", {
  x: 100,      // Good - uses transform
  y: 50,       // Good - uses transform
  rotation: 45, // Good - uses transform
  scale: 1.2,  // Good - uses transform
  // Avoid: left, top, width, height when possible
});

// Enable force3D for GPU acceleration
gsap.to(".element", {
  x: 100,
  force3D: true // Ensures GPU acceleration
});

Use will-change Wisely

// Apply will-change before animation
element.style.willChange = "transform";

gsap.to(element, {
  x: 100,
  onComplete: () => {
    element.style.willChange = "auto"; // Remove after animation
  }
});

Stagger for Multiple Elements

// Always use stagger for multiple elements
gsap.to(".items", {
  opacity: 1,
  y: 0,
  stagger: 0.1, // Prevents all elements animating at once
  duration: 0.5
});

// Advanced stagger options
gsap.to(".grid-items", {
  scale: 1,
  stagger: {
    each: 0.1,
    from: "center",
    grid: "auto"
  }
});

Use Lag Smoothing

// Prevent animation stuttering during CPU spikes
gsap.ticker.lagSmoothing(1000, 16);

Timeline Best Practices

Use Timelines for Complex Sequences

const tl = gsap.timeline({
  defaults: { duration: 0.5, ease: "power2.out" }
});

tl.to(".header", { y: 0, opacity: 1 })
  .to(".content", { y: 0, opacity: 1 }, "-=0.3") // Overlap
  .to(".footer", { y: 0, opacity: 1 }, "-=0.3");

Use Labels for Organization

const tl = gsap.timeline();

tl.addLabel("start")
  .to(".intro", { opacity: 1 })
  .addLabel("middle")
  .to(".main", { x: 100 })
  .addLabel("end")
  .to(".outro", { opacity: 0 });

// Jump to label
tl.play("middle");

Control Timelines

const tl = gsap.timeline({ paused: true });

// Methods
tl.play();
tl.pause();
tl.reverse();
tl.restart();
tl.seek(1.5); // Go to 1.5 seconds
tl.progress(0.5); // Go to 50%

ScrollTrigger Best Practices

Basic ScrollTrigger Setup

gsap.to(".element", {
  x: 500,
  scrollTrigger: {
    trigger: ".element",
    start: "top center",
    end: "bottom center",
    scrub: true,
    markers: false // Enable for debugging only
  }
});

Pin Elements Properly

ScrollTrigger.create({
  trigger: ".panel",
  pin: true,
  start: "top top",
  end: "+=500",
  pinSpacing: true
});

Batch ScrollTriggers for Performance

ScrollTrigger.batch(".items", {
  onEnter: (elements) => {
    gsap.to(elements, {
      opacity: 1,
      y: 0,
      stagger: 0.1
    });
  }
});

React Integration

Use useGSAP Hook

import { useGSAP } from "@gsap/react";

function Component() {
  const containerRef = useRef(null);

  useGSAP(() => {
    gsap.to(".box", { x: 100 });
  }, { scope: containerRef }); // Scopes selectors to container

  return <div ref={containerRef}>...</div>;
}

Cleanup Animations

useGSAP(() => {
  const tl = gsap.timeline();
  tl.to(".element", { x: 100 });

  return () => {
    tl.kill(); // Clean up on unmount
  };
}, []);

Selector Optimization

Cache DOM Selectors

// Bad - queries DOM on every call
gsap.to(".element", { x: 100 });
gsap.to(".element", { y: 50 });

// Good - cache the reference
const element = document.querySelector(".element");
gsap.to(element, { x: 100 });
gsap.to(element, { y: 50 });

Use gsap.utils for Efficiency

// Convert NodeList to Array
const items = gsap.utils.toArray(".items");

// Create reusable selector
const select = gsap.utils.selector(container);
gsap.to(select(".box"), { x: 100 });

Easing

Use Appropriate Eases

// Common eases for UI
gsap.to(".element", { x: 100, ease: "power2.out" }); // Decelerate
gsap.to(".element", { x: 100, ease: "power2.in" });  // Accelerate
gsap.to(".element", { x: 100, ease: "power2.inOut" }); // Both

// Bounce and elastic for playful UI
gsap.to(".element", { y: 0, ease: "bounce.out" });
gsap.to(".element", { scale: 1, ease: "elastic.out(1, 0.3)" });

SVG Animation

Animate SVG Properties

gsap.to("path", {
  strokeDashoffset: 0,
  duration: 2,
  ease: "none"
});

gsap.to("circle", {
  attr: { r: 50, cx: 200 },
  duration: 1
});

Complex Animations

Use MotionPath for Path Animation

import { MotionPathPlugin } from "gsap/MotionPathPlugin";
gsap.registerPlugin(MotionPathPlugin);

gsap.to(".element", {
  motionPath: {
    path: "#path",
    align: "#path",
    autoRotate: true
  },
  duration: 5
});

Debugging

Use Markers During Development

ScrollTrigger.defaults({
  markers: process.env.NODE_ENV === "development"
});

Debug Timeline Progress

tl.eventCallback("onUpdate", () => {
  console.log(tl.progress());
});

Best Practices Summary

1. Always use transforms over positional properties
2. Use stagger for animating multiple elements
3. Leverage timelines for complex sequences
4. Cache DOM selectors
5. Use useGSAP hook in React
6. Clean up animations on component unmount
7. Enable lag smoothing for smooth playback
8. Test on actual devices, especially mobile