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Ramp·Frontend Engineer·Technical Phone Screen·Intermediate

Intermediate
May 2026

Summary

Frontend engineering round at Ramp, one coding problem focused on React animation behavior. Pretty niche stuff, not your typical leetcode grind, which I appreciated but also wasn't fully ready for.

Questions Asked (1)

Q1

Build a React component that reveals a string character by character using a typewriter animation with setTimeout or setInterval inside useEffect. The animation must run exactly once for the component's lifetime, even under React strict mode's double-invocation behavior.

Technical Trade-offsSystem Design
Author's notes

This is where I tripped up first.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the requirements and constraints, then outline a solution using useEffect with a cleanup function to handle strict mode. Emphasize the importance of idempotent effects and demonstrate how to ensure the animation runs once by using a ref or proper cleanup.

Pro tip: Use a ref to track whether the animation has already started, and always clear the timer in the cleanup function to prevent memory leaks and duplicate animations. This shows you understand React's lifecycle and strict mode nuances.

1. Clarify Requirements

Restate the problem to ensure you understand the need for a typewriter effect that runs once, even in strict mode. Ask about edge cases like component unmounting or prop changes.

2. Design the Effect

Plan to use useEffect with an empty dependency array to run once on mount. Use a ref to guard against double invocation in strict mode, and set up a timer with setInterval or setTimeout.

3. Implement Cleanup

Return a cleanup function from useEffect that clears the timer. This prevents memory leaks and ensures that if the component unmounts, the animation stops.

4. Handle Strict Mode

Explain that in strict mode, effects run twice (mount, unmount, mount). Use a ref to track if the animation has already started, so the second mount doesn't restart it.

5. Test and Validate

Mention testing the component in strict mode to verify the animation runs only once. Discuss potential pitfalls like stale closures and how to avoid them.

Key Points to Mention

  • useEffect with empty dependency array for mount-only execution
  • Cleanup function to clear timers and prevent memory leaks
  • Using useRef to guard against double invocation in strict mode
  • Understanding React strict mode's double-invocation of effects
  • State management for the displayed string (e.g., useState)
  • Choosing between setTimeout and setInterval for character-by-character animation

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.