Performance & Optimization

Question 1

Why is using the index as a key in React lists a bad idea?

Answer 1

If the list order changes, it can lead to performance issues and bugs as React uses keys to reconcile the DOM.

Question 2

How can you prevent a component from re-rendering?

Answer 2

Using React.memo() for functional components or shouldComponentUpdate lifecycle method for class components.

Question 3

Name some tools you can use to diagnose performance issues in React apps.

Answer 3

React DevTools, Chrome DevTools, the Profiler API, and Lighthouse.