Frontend Developer Intern

Build a mini spreadsheet application inspired by Microsoft Excel where users can interact with a grid of editable cells. The application should support features like cell editing, keyboard navigation, basic formulas such as SUM and AVG, and operations like sorting and filtering. The goal is to demonstrate efficient state management and optimized rendering while handling a large number of dynamic elements.

• Explain how reconciliation works in React.
• You notice a page re-renders too often. How would you debug unnecessary re-renders and optimize performance?
• How does the JavaScript event loop affect UI rendering and responsiveness in the browser?
• What is the difference between debouncing and throttling? Where would you use each in a real frontend app?
• How would you implement infinite scrolling efficiently without killing performance?
• How would you handle authentication and protected routes in a frontend app securely?
• Explain CSS stacking context with a real-world bug example where z-index doesn’t work.

You are asked to build a spreadsheet-like grid (like Excel) in React.
What challenges would you face in:
performance
state management
rendering large datasets