I spent too long on the column math and not enough time explaining my breakpoint strategy out loud.
Start by clarifying requirements and constraints, then outline a mobile-first architecture using CSS custom properties and a 12-column grid. Explain how you would implement container, row, and col-* classes with breakpoints, gutters, and nesting, and discuss trade-offs like specificity, performance, and maintainability.
Pro tip: Emphasize that you would use CSS custom properties for breakpoints and gutters to make the system easily themeable and maintainable, and mention how you would handle edge cases like nested rows and responsive gutters without bloating the CSS.
Ask about browser support, desired breakpoints, whether a build step is allowed, and any performance or accessibility requirements. Confirm that the goal is to replicate Bootstrap-like utilities without external frameworks.
Define a mobile-first 12-column grid using CSS Grid or Flexbox. Use CSS custom properties for breakpoints and gutters, and plan classes like .container, .row, and .col-{breakpoint}-{size}.
Write the CSS for container (max-width, padding), row (display: flex, flex-wrap, negative margins for gutters), and columns (flex-basis, max-width, padding for gutters). Include responsive modifiers via media queries.
Explain how nested rows work by resetting negative margins and ensuring columns inside columns behave correctly. Discuss gutter strategies: padding on columns with negative margins on rows, or CSS Grid gap.
Compare Flexbox vs CSS Grid, talk about specificity and class naming, and how to keep the system reusable and scalable. Mention potential performance impacts and how to mitigate them.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.
Accessibility is one of those things I think I know better than I actually do.
Start by outlining the utility class system's design tokens (spacing, colors, typography) and how they map to component styles. Then, walk through building each component with semantic HTML and ARIA attributes, explaining how the utility classes enable consistent, accessible styling. Finally, demonstrate validation messages with proper live regions and error associations.
Pro tip: Emphasize that accessibility is not an afterthought but integrated into the utility system—e.g., using utility classes to enforce focus styles and color contrast. Also, mention testing with screen readers and automated tools like axe to show practical validation.
Explain the utility class system's tokens for spacing, color, typography, and states (focus, hover, disabled). Highlight how these tokens ensure consistency and accessibility (e.g., color contrast ratios).
Use <nav> with aria-label, <ul> for links, and skip-to-content link. Apply utility classes for layout and focus styles, ensuring keyboard navigability.
For buttons, use <button> with clear labels and utility classes for states. For inputs, use <label> with for attribute, and utility classes for error/success states. Include aria-describedby for validation messages.
Use aria-live regions for dynamic errors, associate messages with inputs via aria-describedby, and style with utility classes. Ensure messages are announced by screen readers.
Mention testing with keyboard navigation, screen readers (e.g., NVDA, VoiceOver), and automated tools (axe, Lighthouse). Use utility classes to quickly adjust styles based on feedback.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.
This follow-up was the more interesting part of the interview.
Start by clarifying requirements and constraints, then walk through the form submission lifecycle, explicitly defining each state and the transitions between them. For each state, describe the UI treatment, error classification (retryable vs non-retryable), and the telemetry events you'd emit to measure success and failure. Conclude by discussing trade-offs and how you'd validate the design.
Pro tip: Tie your telemetry to business metrics like order completion rate and show how you'd use it to detect and diagnose issues in production. Also, mention idempotency keys to prevent duplicate submissions on retry, which is critical for payment flows.
Ask about the form's purpose (e.g., payment, signup), expected load, and any compliance requirements. Confirm the async submission mechanism (e.g., REST API, GraphQL) and whether offline support is needed.
Enumerate all possible states: idle, validating, submitting, success, retryable error, non-retryable error, and timeout. Describe how the UI reflects each state and the allowed transitions (e.g., from submitting to retryable error, then back to submitting on retry).
Classify errors into retryable (network, 5xx, 429) and non-retryable (4xx validation, 401, 403). Specify retry strategies (exponential backoff with jitter, max attempts) and how to surface errors to users with clear messaging and recovery actions.
Define key events (submission_started, submission_succeeded, submission_failed) with properties like error_type, retry_count, latency, and form_id. Explain how to aggregate these into metrics (success rate, error rate, p95 latency) and set up alerts.
Address trade-offs such as optimistic UI vs. pessimistic, retry aggressiveness vs. server load, and telemetry granularity vs. privacy. Describe how you'd test the design (unit, integration, chaos) and iterate based on telemetry.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.