Design and Performance Decisions

🚀 Performance Optimization

1. List Virtualization (React Virtuoso)

We used React Virtuoso to handle potential large datasets efficiently.

• Problem: Standard rendering creates a DOM node for every single item, which degrades performance and increases memory usage as the list grows.
• Solution: Virtuoso implements "Windowing," rendering only the items currently visible in the viewport. This keeps the DOM lightweight and ensures a smooth 60 FPS scrolling experience regardless of the total number of items.

2. Stable Function Identities (useCallback)

The handleComplete function is wrapped in a useCallback hook.

• Reasoning: In React, functions are re-created on every render. By using useCallback, we maintain the same function instance across re-renders. This is crucial when passing callbacks to memoized child components to prevent them from breaking their memoization.

3. Component Memoization (React.memo)

The TodoItem component is designed to be wrapped in React.memo.

• Reasoning: Combined with useCallback, this ensures that only the specific item being updated (e.g., toggling completion) re-renders. The rest of the items in the virtualized list remain untouched, saving significant CPU cycles.