🌐 Frontend Dev

Type alias for a function with optional param and default value

Tests whether you know function type expressions cannot encode default values. A great answer writes (s: string, n?: number) => boolean, explains defaults are implementation-only, and notes parameter names are required.

How do you type a function with two possible response shapes?

This checks TypeScript union types for API responses. Define a union of Product[] and a message object, use a type guard to narrow it at runtime, and return that.

Define a User object shape: interface vs type alias?

Tests structural typing and API contracts. Good answer: interface for API objects because it merges; type alias for unions. Forced: declaration merging needs interface; discriminated unions need type. Red flag: claiming performance differences.

How do you select by ID and class, and what is returned?

This tests basic DOM API knowledge and awareness of live collections. Use document.getElementById for IDs and document.getElementsByClassName for classes, which returns a live HTMLCollection. A red flag is calling the result a static Array or NodeList.

easy1 min read

What happens when you declare var globally versus let or const?

In a classic browser script, global var creates a non-configurable window property. Global let/const use lexical bindings instead. Modules behave differently.

What is the fundamental difference between window and document?

Window is the browser tab and global scope; document is the object-oriented DOM representation of the loaded page.

Explain what TypeScript's type inference is and show an inferred variable declaration

This tests whether you understand TypeScript deduces types without annotations. A strong answer defines inference as deriving types from values and gives an example like let x = 3 inferring number. A red flag is claiming explicit types are required.

Declare a string name and an array of lucky numbers in TypeScript

Declare the name with a lowercase string type and the lucky numbers as number[] or Array<number>.

Kent C. Dodds Fixes Accidental Monorepo with Workspaces

Kent C. Dodds consolidated four deployable apps into a proper npm workspace, deleting three nested lockfiles and adding minimal Nx caching. The migration exposed hardcoded paths and invalid package aliases that broke production once Node enforced package…

Cloudflare Sandboxes Cut Container Heartbeat Plumbing

Kent C. Dodds replaced Cloudflare Containers with Sandboxes, deleting heartbeat and shutdown logic for his FFmpeg pipeline. PR #729 uses one-shot exec() inside the existing queue worker, cutting deploy surface and eliminating long-lived service orchestration.

Kent C. Dodds Adds SQLite FTS5 to Vector Search

Kent C. Dodds added SQLite FTS5 to Vectorize embeddings after semantic search missed exact matches like "React Testing Library." The hybrid pipeline uses Reciprocal Rank Fusion. If your search fails on API names, add BM25 backup, not bigger embedding models.

Vercel Connect replaces env tokens with runtime OIDC

Vercel Connect Public Beta replaces static env tokens with short-lived, task-scoped credentials exchanged at runtime via OIDC. Agents request least-privilege access per job instead of holding long-lived shared secrets, eliminating manual rotation when…

Vercel ships AI Gateway, Workflow SDK, and Sandbox for agents

Vercel Agent Stack unifies hundreds of models, durable workflows, and isolated microVMs for production agents. One endpoint routes across providers, checkpoints resume failed runs, and sandboxes isolate unreviewed code.

Vercel Ship 2026: agent stack, eve framework, and microservices

Vercel Ship 2026 unveils open-source eve framework and Vercel Services for microservices July 1. Vercel is repositioning as agentic infrastructure with Connect credentials and expanded Python backends. Evaluate if your next agent deploys here instead of AWS.

Next.js 16.2 brings 67-100% faster server Fast Refresh

Next.js 16.2 Turbopack brings Server Fast Refresh to Node.js, cutting reload times 67-100% and compile times 400-900%. Only changed modules reload, not whole chains. WASM Workers, SRI, and dynamic import tree shaking land; upgrade to cut dev latency.

Next.js 16.2 adds agent-native dev tooling

Next.js 16.2 bundles version-matched docs with create-next-app, hitting 100% on framework evals versus 79% without. Browser errors now forward to terminal and a dev server lock file prevents agent confusion. Upgrade if you use AI coding agents.

Next.js 16.2 ships stable Adapter API for all platforms

Next.js 16.2 ships a stable Adapter API co-built with OpenNext, Netlify, and Cloudflare. The typed build contract lets any platform target full framework fidelity using the same public hooks Vercel uses. Stop reverse-engineering build output.

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.

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.