performance-optimization（性能优化）

Performance Optimization

Diagnose and fix slow or janky animations using Disney's 12 principles.

Problem Indicators

• Frame rate drops below 60fps
• Stuttering or choppy motion
• UI feels sluggish
• Battery drain on mobile
• Layout thrashing

Diagnosis by Principle

Straight Ahead vs Pose-to-Pose

Issue: Calculating every frame in real-time Fix: Use pose-to-pose (keyframe) animation. Let the browser interpolate between states using CSS transitions or will-change.

Timing

Issue: Too many simultaneous animations Fix: Stagger animations. Offset start times by 50-100ms to reduce concurrent calculations.

Secondary Action

Issue: Too many secondary effects Fix: Remove non-essential secondary animations on low-power devices. Use prefers-reduced-motion query.

Solid Drawing

Issue: Animating expensive properties (width, height, top, left) Fix: Only animate transform and opacity. These are GPU-accelerated and skip layout/paint.

Staging

Issue: Animating off-screen elements Fix: Only animate what's visible. Use Intersection Observer to pause off-screen animations.

Quick Fixes

1. Replace JS animations with CSS - Browser-optimized
2. Use transform instead of position properties - GPU layer
3. Add will-change sparingly - Hints to browser
4. Reduce simultaneous animations - Stagger or sequence
5. Lower animation complexity on mobile - Detect device capability

Troubleshooting Checklist

• Check DevTools Performance tab for long frames
• Verify animations use transform/opacity only
• Count simultaneous animations (keep under 3-4)
• Test on lowest-spec target device
• Check for layout thrashing (forced reflows)
• Verify will-change isn't overused
• Test with CPU throttling enabled
• Check if animations pause when tab is hidden

Code Pattern

/* Fast */
.element {
  will-change: transform;
  transition: transform 200ms ease-out;
}
.element:hover {
  transform: translateY(-4px);
}

/* Slow - avoid */
.element:hover {
  top: -4px; /* Triggers layout */
}