Easy interview questions in Frontend Dev, page 7
What is tsconfig strict, and which sub-flag to relax for legacy?
Tests strict as a master switch and migration pragmatism. Strong answers name strictNullChecks or noImplicitAny as the first to relax in legacy code, trading null-safety for fewer errors. Red flag: disabling strict entirely instead of a targeted sub-flag.
What is Next.js Middleware and a real-world auth use case?
This tests request interception before a route renders. A good answer defines Middleware as pre-request code using NextRequest and NextResponse, often on the Edge Runtime, with auth redirects as an example.
How do you enable basic i18n routing in Next.js?
This tests your knowledge of the built-in Pages Router i18n configuration in next.config.js. A good answer exports an i18n object with locales array, defaultLocale, and optionally localeDetection.
What is the Virtual DOM's role during a Vue state update?
Tests your grasp of Vue's reactive render pipeline. A strong answer: state change triggers a new virtual DOM tree; runtime diffs it against the old tree to apply only necessary real DOM updates. Red flag: saying virtual DOM updates browser DOM directly.
How do you add TypeScript types for a library without bundled types?
This tests the DefinitelyTyped @types workflow. Install @types/package as a dev dependency via npm or yarn, skipping it when the library already bundles .d.ts files. A red flag is suggesting manual declarations or extra tooling before checking DefinitelyTyped.
What is SSR and what are its advantages over a client-side SPA?
This tests server-client rendering trade-offs. A strong answer defines SSR as server HTML generation plus client hydration, citing faster time-to-content, better SEO for async data, and unified component logic.
How do you write a minimal dom-utils.d.ts for a JS function?
Tests bridging untyped JavaScript into TypeScript via ambient module declarations. A strong answer declares a module matching the file path and exports the function with a typed signature. Red flag: suggesting rename to .ts or using any.
How do you manage Next.js env variables on Vercel and use NEXT_PUBLIC_?
Set DB strings in Vercel dashboard without NEXT_PUBLIC_; consume in server code only. NEXT_PUBLIC_ inlines values into the browser JS bundle, leaking them to all users.
What is the purpose of +page.server.js in SvelteKit?
Exclusively server-side load feeding the data prop, used for secrets like DB queries and private env vars.
How would you implement a basic protected route in React?
Hold auth in useState, pass user to protected components, and return Navigate to login when absent.
Would you use getServerSideProps or getStaticProps for private user data?
Tests SSR vs SSG privacy. Use getServerSideProps: it runs per-request with auth cookies. getStaticProps bakes HTML/JSON at build time, leaking private data across users. Red flag: suggesting ISR or revalidation for authenticated data.
What are keys in React lists and why are they important?
Whether you understand React's reconciliation identity tracking. Keys are unique identifiers that let React match items across renders, preserving DOM state and avoiding unnecessary recreation.
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