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Salesforce·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
May 2026

Summary

Frontend coding round at Salesforce where they had me build a traffic light component from scratch. Pretty standard UI exercise but there's more to get right than it looks.

Questions Asked (1)

Q1

Build a cycling traffic light using HTML, CSS, and JavaScript. Three circles, one active at a time, cycling red then green then yellow with configurable durations per color.

Technical Trade-offsAPI & Integrations
Author's notes

I got the basic structure up pretty fast but the timer logic tripped me up more than I expected.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and edge cases, then outline a clean architecture separating state, configuration, and rendering. Implement the cycling logic with configurable durations, ensuring smooth transitions and accessibility. Finally, discuss trade-offs and potential integrations, tying back to Salesforce's ecosystem.

Pro tip: Demonstrate maturity by proactively addressing accessibility (ARIA roles, color-blindness) and performance (using requestAnimationFrame or CSS transitions instead of setInterval). This shows you think beyond the happy path.

1. Clarify Requirements

Ask questions to understand expected behavior: Should durations be configurable via UI or code? What happens on page load? Any accessibility requirements? This ensures alignment before coding.

2. Design Architecture

Outline a simple state machine with states (red, green, yellow) and transitions. Separate configuration (durations) from logic and rendering. Consider using a class or module pattern for maintainability.

3. Implement Core Logic

Write JavaScript to cycle through states with configurable durations. Use setTimeout or requestAnimationFrame for timing, and update the DOM to reflect the active light. Ensure only one light is active at a time.

4. Enhance with CSS and Accessibility

Style the circles with CSS, using classes to indicate active state. Add ARIA attributes (e.g., role='img', aria-label) and ensure sufficient color contrast. Consider adding a pause/resume control for usability.

5. Discuss Trade-offs and Extensions

Talk about trade-offs: setInterval vs. recursive setTimeout, CSS transitions vs. JS animations. Mention potential integrations (e.g., Salesforce Lightning Web Components) and how you'd test the component.

Key Points to Mention

  • State management: using a finite state machine or simple state variable to track current light.
  • Configurable durations: exposing an API or configuration object to set timings per color.
  • Timing mechanisms: comparing setInterval, setTimeout, and requestAnimationFrame for accuracy and performance.
  • Accessibility: ARIA roles, labels, and color contrast for visually impaired users.
  • Separation of concerns: keeping HTML structure, CSS styling, and JavaScript logic distinct.
  • Testing and extensibility: unit tests for state transitions, and potential integration with frameworks like Lightning Web Components.

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