Build a Stateful Calculator
Company: Zoox
Role: Frontend Engineer
Category: Software Engineering Fundamentals
Difficulty: hard
Interview Round: Onsite
Implement a calculator UI component.
Requirements:
- Support digit input and the operators `+`, `-`, `*`, and `/`.
- Support `=` to finalize the current calculation.
- Support a reset action that clears the calculator state.
- The display must update correctly during chained operations, not only at the very end.
Example behavior:
- Input: `1`, `+`, `100`, `+`, `20`, `=`
- When the second `+` is pressed, the display should immediately show `101`.
- After `=` is pressed, the display should show `121`.
Explain how you would model the calculator state and implement operator chaining so the UI always shows the correct current value.
Quick Answer: This question evaluates a candidate's ability to model and manage UI state, handle event-driven input, and implement correct operator chaining in a calculator component, testing frontend state management and user interface behavior within the software engineering fundamentals domain.