#React

What is reconciliation in React? Explain how React determines what to render efficiently.

Discuss the differences between Virtual DOM and Real DOM in React. Why is the Virtual DOM faster?

Design a system of concurrent progress bars that handle multiple tasks running in parallel. Implement features for starting, pausing, and resetting actions, ensuring independent states for each progress bar. Use simulated asynchronous tasks like setInterval or Promises.

Define controlled and uncontrolled components in React. What are the benefits and drawbacks of each approach?

Design a reusable Star Rating component where clicking sets the rating, hovering previews the rating, and it supports keyboard navigation. How would you handle controlled vs uncontrolled components and prevent unnecessary re-renders? What accessibility roles would you add, and how would you write tests for it?