Interview questions in Frontend Dev, page 10
What are the two principles of OOCSS?
Separate structure from skin, and separate container from content; this lets visual themes and layout be mixed and reused independently.
What attribute scopes styles to a Vue component?
This tests knowledge of Vue's style encapsulation. Add the scoped attribute to the style tag; Vue adds a unique data attribute to elements and selectors. A red flag is suggesting manual BEM or claiming scoped styles never affect child components.
How do you type an async function return in TypeScript?
This tests if you know async functions always return Promise<T>. A great answer: annotate Promise<User>, return User from the body, and note TypeScript implicitly wraps it. A red flag is omitting Promise and typing the return as just User.
How would you implement real-time client-side validation in React?
Tests state-driven UI thinking over imperative DOM updates. A strong answer uses a status enum like typing or error, derives validation from state instead of redundant booleans, and conditionally renders feedback.
How custom properties enable dynamic theming
Custom properties cascade and resolve live, so redefining them on a scope or data attribute reskins everything via var().
What is Angular's default style encapsulation mechanism called?
Tests if you know Angular's default view encapsulation. A strong answer names ViewEncapsulation.Emulated, describes the unique attribute selector rewrite, and warns that global styles still pierce inward.
How would you prevent search-as-you-type race conditions with AbortController?
Abort the previous request before each new keystroke, pass the fresh signal into fetch, and ignore the AbortError.
Advantages of dedicated React form libraries over manual state
Your grasp of the hidden costs of fully controlled form state in React. Mention re-render reduction via refs, declarative validation, less boilerplate, and custom input support.
Explain the inverted triangle of ITCSS
ITCSS orders layers from far-reaching low-specificity (settings, tools, generic) down to localized high-specificity (components, utilities), so specificity climbs gradually.
How does Svelte scope component styles during compilation?
The compiler adds a unique attribute to component elements and rewrites selectors to target it, isolating styles.
Implement inSequence(tasks) to execute promise-returning functions sequentially
Tests async/await control flow versus Promise.all parallelism. A strong answer uses a for-of loop with await inside an async function, accumulates results in order, and stops cleanly on rejection. Red flag: suggesting Promise.all or forEach with await.
How do you use a Server Action for form submission and useFormState?
Tests server-client form state orchestration. Outline: write a Server Action that validates and returns errors; pass it to useFormState for state; wire to form action and use useFormStatus for pending UI.
Should a component own its outer spacing?
Components own internal padding but should not own external margin; the parent or layout owns spacing between siblings, keeping components context-independent.
Compare Angular's three ViewEncapsulation modes and give a use case.
This tests style isolation tradeoffs. Emulated scopes CSS with unique attributes, ShadowDom uses native shadow roots, and None disables scoping. Switch to ShadowDom for strict boundaries or None for global themes.
Write a fetch call and log JSON from the Response
This tests async HTTP literacy and fetch's two-stage promise resolution. A strong answer awaits fetch, then awaits response.json(), logs result, and notes fetch does not throw on 4xx/5xx.
Optimize a large form with frequent state updates
Tests render propagation and memoization discipline. Strong answers note parent updates re-render children, extract inputs to localize state, useMemo for derived values, and stable callbacks. Red flag: useMemo everywhere without component boundaries.
Utility-first versus semantic CSS trade-offs
Utility-first gives speed, small purged bundles, and no naming overhead but verbose markup; semantic BEM gives readable markup and clear boundaries but naming and dead-CSS risk.
What deep selector pierces Vue scoped styles, and why use it cautiously?
This tests Vue scoped CSS encapsulation. Use :deep() to target child internals from a scoped block, but it breaks encapsulation and creates brittle coupling. A red flag is recommending deprecated /deep/ or unscoped global styles.
How would you modify fetch to handle HTTP error statuses?
Verify response.ok in then and throw if false, then catch network failures separately.
Design a multi-step wizard form pattern in React
Shared state, step validation, and resilient navigation. A great answer uses one form instance with per-step Zod schemas, a context stepper, and localStorage persistence. Red flag: isolated forms per step that lose data on navigation.
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