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Amazon·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
May 2026

Summary

Amazon SWE coding round with a front-end focused problem. Pretty straightforward on the surface but there were enough moving parts to trip you up if you weren't careful about state management.

Questions Asked (1)

Q1

Build a wishlist feature in vanilla JavaScript that shows 5 product rows initially, each with a toggle button that switches between 'Add to wishlist' and 'Remove from wishlist' states. Also add a 'load more' button that appends 5 more rows at a time up to a max of 30, and display a live row count at the top.

API & IntegrationsTechnical Trade-offs
Author's notes

More to juggle than it looks.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and edge cases, then outline a clean architecture using event delegation and a central state object. Walk through the implementation step-by-step, emphasizing performance, accessibility, and how you would test and extend it.

Pro tip: Mention that you would use event delegation on a container to handle all toggle and load-more clicks, which improves performance and simplifies dynamic row management. Also, discuss how you would persist wishlist state using localStorage or a backend API to align with Amazon's customer-centric features.

1. Clarify Requirements and Edge Cases

Ask questions to confirm initial row count, max rows, toggle behavior, and whether state should persist. Identify edge cases like rapid clicking, loading beyond max, and accessibility needs.

2. Design State and Data Model

Define a central state object to track total rows, wishlist items, and loading status. Plan how to render rows dynamically and update the count efficiently.

3. Implement Core Logic with Event Delegation

Write functions to create rows, toggle wishlist state, and append more rows. Use event delegation on a parent container to handle clicks for both toggle buttons and the load more button.

4. Optimize and Handle Edge Cases

Ensure the load more button disables at 30 rows, prevent duplicate event listeners, and use efficient DOM updates. Consider debouncing rapid clicks and maintaining accessibility with ARIA attributes.

5. Test and Discuss Trade-offs

Outline a testing strategy (unit, integration, manual) and discuss trade-offs like client-side vs server-side state, performance implications, and scalability.

Key Points to Mention

  • Event delegation to handle dynamic elements efficiently
  • Centralized state management to keep UI in sync
  • Accessibility considerations (ARIA labels, keyboard navigation)
  • Performance optimizations (document fragment, debouncing)
  • Persistence options (localStorage, API integration)
  • Testing approach and trade-offs (e.g., re-rendering vs direct DOM manipulation)

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