Performance Optimization Basics

Understanding React's rendering behavior and optimization techniques is crucial for building fast applications. This lesson covers the fundamentals of React.memo, useMemo, and useCallback.

Understanding Re-renders

React re-renders components when their state or props change. Understanding this is key to optimization.

React.memo Concept

React.memo prevents re-renders when props haven't changed.

useMemo Concept

useMemo memoizes expensive calculations, recalculating only when dependencies change.

useCallback Concept

useCallback memoizes functions, preventing new function references on every render.

When to Optimize

Not all components need optimization. Here's how to decide.

Exercise: Implement Memoization

Exercise: Shallow Comparison

Exercise: Optimized Component

Key Takeaways

1. Re-renders happen - When state or props change, components re-render
2. React.memo - Prevents re-renders when props haven't changed (shallow comparison)
3. useMemo - Caches expensive calculations, recalculates when dependencies change
4. useCallback - Caches function references, prevents new functions on each render
5. Measure first - Don't optimize prematurely; profile and identify bottlenecks
6. Shallow comparison - React compares references, not deep values