UI Framework Performance Guide

1. Key Performance Metrics

Initial Load Time

// Example of measuring initial load
const startTime = performance.now();
// Your app initialization
const endTime = performance.now();
console.log(`Load time: ${endTime - startTime}ms`);

Key metrics to monitor:

• Time to First Byte (TTFB) < 200ms
• First Contentful Paint (FCP) < 1.8s
• Time to Interactive (TTI) < 3.8s

Bundle Size Impact

// Example calculation
const bundleSize = 500; // KB
const downloadTime = bundleSize / (internetSpeed / 8); // seconds
// 500KB / (5Mbps / 8) = 0.8 seconds

2. Performance Warning Signs

1. Memory Leaks

// Bad: Memory leak
class Component {
  constructor() {
    this.data = new Array(1000000);
    window.addEventListener("resize", this.handleResize);
  }
  // Missing cleanup!
}

// Good: Proper cleanup
class Component {
  constructor() {
    this.data = new Array(1000000);
    this.handleResize = this.handleResize.bind(this);
    window.addEventListener("resize", this.handleResize);
  }

  destroy() {
    window.removeEventListener("resize", this.handleResize);
    this.data = null;
  }
}

2. Slow Rendering

// Bad: Unnecessary re-renders
function BadComponent() {
  const [count, setCount] = useState(0);
  const [unrelated, setUnrelated] = useState(0);

  // Re-renders on every state change
  return <div>{count}</div>;
}

// Good: Memoized component
const GoodComponent = React.memo(function GoodComponent({ count }) {
  return <div>{count}</div>;
});

3. Framework Selection Criteria

1. Project Size and Complexity

Project Size	Recommended Framework	Bundle Size	Learning Curve
Small	Vue.js	~30KB	Low
Medium	React	~40KB	Medium
Large	Angular	~130KB	High

2. Performance Budget

// Example performance budget
const performanceBudget = {
  bundleSize: 500, // KB
  loadTime: 3000, // ms
  memoryUsage: 50, // MB
};

4. Scaling Considerations

1. Component Count Impact

// Example calculation
const componentMemory = 100; // KB per component
const totalComponents = 1000;
const totalMemory = componentMemory * totalComponents; // 100MB

2. User Load Impact

// Example calculation
const usersPerSecond = 100;
const memoryPerUser = 50; // MB
const totalMemory = usersPerSecond * memoryPerUser; // 5GB

5. Performance Monitoring Tools

1. Chrome DevTools

// Performance recording
console.time("operation");
// Your code here
console.timeEnd("operation");

// Memory snapshot
console.memory; // Shows heap size

2. Lighthouse

# Run Lighthouse audit
lighthouse https://your-app.com --view

6. Framework Comparison Matrix

Framework	Initial Load	Runtime Performance	Memory Usage	Best For
React	Fast	High	Medium	Large apps
Vue	Very Fast	High	Low	Small-medium apps
Angular	Medium	Medium	High	Enterprise apps

7. Performance Optimization Checklist

1. Bundle Size

   • Use code splitting
   • Implement lazy loading
   • Optimize images

2. Render Performance

   • Implement virtualization for long lists
   • Use memoization
   • Avoid unnecessary re-renders

3. Memory Management

   • Clean up event listeners
   • Clear large data structures
   • Use WeakMap/WeakSet for caching

8. Real-World Example

// Performance monitoring setup
const performanceMonitor = {
  metrics: {
    renderTime: [],
    memoryUsage: [],
    bundleSize: 0,
  },

  startMonitoring() {
    // Monitor render times
    setInterval(() => {
      const start = performance.now();
      // Your app's render cycle
      const end = performance.now();
      this.metrics.renderTime.push(end - start);
    }, 1000);

    // Monitor memory
    setInterval(() => {
      this.metrics.memoryUsage.push(performance.memory.usedJSHeapSize);
    }, 5000);
  },

  getAverageRenderTime() {
    return (
      this.metrics.renderTime.reduce((a, b) => a + b) /
      this.metrics.renderTime.length
    );
  },
};

9. Decision Making Process

1. Project Requirements

   • Team size and experience
   • Project timeline
   • Performance requirements

2. Technical Constraints

   • Browser support
   • Mobile requirements
   • Integration needs

3. Performance Budget

   • Maximum bundle size
   • Maximum load time
   • Memory constraints

10. Common Performance Issues and Solutions

1. Slow Initial Load

• Use code splitting
• Implement lazy loading
• Optimize bundle size

2. High Memory Usage

• Implement proper cleanup
• Use memory-efficient data structures
• Monitor memory leaks

3. Slow Rendering

• Use virtualization for lists
• Implement memoization
• Optimize re-renders

11. Performance Testing Tools

1. Chrome DevTools

   • Performance tab
   • Memory tab
   • Network tab

2. Lighthouse

   • Performance audit
   • Accessibility audit
   • Best practices audit

3. WebPageTest

   • Load time testing
   • Performance metrics
   • Waterfall charts

12. Best Practices

1. Regular Monitoring

   • Set up performance budgets
   • Monitor key metrics
   • Track user feedback

2. Optimization

   • Regular code reviews
   • Performance testing
   • User experience monitoring

3. Documentation

   • Performance requirements
   • Optimization strategies
   • Monitoring procedures