Module 23: Performance Optimization

Overview

This module covers JavaScript performance optimization techniques at the application level. Learn to identify bottlenecks, optimize code, and build fast, responsive applications.

Learning Objectives

By the end of this module, you will be able to:

• •Profile and identify performance bottlenecks
• •Optimize JavaScript execution
• •Implement efficient rendering patterns
• •Use caching and memoization effectively
• •Build performant web applications

Prerequisites

• •Module 12: Execution Context (call stack, event loop)
• •Module 17: DOM Manipulation (rendering)
• •Module 19: Advanced DOM/Browser APIs (observers)
• •Module 24: Engine Internals (recommended)

Sections

23.1 Performance Basics

• •Performance metrics (FCP, LCP, TTI, TBT)
• •Profiling with DevTools
• •Identifying bottlenecks
• •Performance budgets
• •Measuring performance

23.2 JavaScript Optimization

• •Algorithm complexity
• •Loop optimization
• •Object and array patterns
• •String manipulation
• •Memory-efficient patterns

23.3 Rendering Performance

• •Critical rendering path
• •Avoiding layout thrashing
• •requestAnimationFrame
• •Virtual scrolling
• •Debouncing and throttling

23.4 Network Performance

• •Code splitting
• •Lazy loading
• •Prefetching strategies
• •Caching strategies
• •Service workers

23.5 Capstone Projects

• •Performance audit project
• •Optimization case studies
• •Benchmarking exercises
• •Real-world optimization

Performance Metrics Overview

┌────────────────────────────────────────────────────────────────────────────┐
│                    Core Web Vitals & Performance Metrics                   │
├────────────────────────────────────────────────────────────────────────────┤
│                                                                            │
│   Loading Performance                                                       │
│   ┌─────────────────────────────────────────────────────────────────┐      │
│   │  FCP (First Contentful Paint)     < 1.8s   ✅ Good              │      │
│   │  LCP (Largest Contentful Paint)   < 2.5s   ✅ Good              │      │
│   │  TTI (Time to Interactive)        < 3.8s   ✅ Good              │      │
│   └─────────────────────────────────────────────────────────────────┘      │
│                                                                            │
│   Interactivity                                                             │
│   ┌─────────────────────────────────────────────────────────────────┐      │
│   │  INP (Interaction to Next Paint)  < 200ms  ✅ Good              │      │
│   │  TBT (Total Blocking Time)        < 200ms  ✅ Good              │      │
│   └─────────────────────────────────────────────────────────────────┘      │
│                                                                            │
│   Visual Stability                                                          │
│   ┌─────────────────────────────────────────────────────────────────┐      │
│   │  CLS (Cumulative Layout Shift)    < 0.1    ✅ Good              │      │
│   └─────────────────────────────────────────────────────────────────┘      │
│                                                                            │
└────────────────────────────────────────────────────────────────────────────┘

Optimization Techniques Quick Reference

File Structure

Module-23-Performance-Optimization/
├── README.md
├── 23.1-Performance-Basics/
│   ├── README.md
│   ├── examples.js
│   └── exercises.js
├── 23.2-JavaScript-Optimization/
│   ├── README.md
│   ├── examples.js
│   └── exercises.js
├── 23.3-Rendering-Performance/
│   ├── README.md
│   ├── examples.js
│   └── exercises.js
├── 23.4-Network-Performance/
│   ├── README.md
│   ├── examples.js
│   └── exercises.js
└── 23.5-Capstone-Projects/
    ├── README.md
    ├── examples.js
    └── exercises.js

Best Practices

1. •Measure first - Profile before optimizing
2. •Focus on impact - Optimize the bottlenecks
3. •Set budgets - Define performance targets
4. •Test on real devices - Not just dev machines
5. •Monitor continuously - Performance regresses

Next Steps

After completing this module, proceed to:

• •Module 24: JavaScript Engine Internals (low-level optimization)