Web APIs

Web API interviews explore how the browser exposes networking, persistence, background work, observation, and cryptography beyond the language core.

Subtopics: Fetch, Web Storage, IndexedDB, service workers, web workers, IntersectionObserver, ResizeObserver, BroadcastChannel, and Web Crypto.

On interviews: compare storage options by sensitivity, when workers help versus hurt, and how observers replace polling.

Common pitfalls: fetch without checking response.ok, tokens in localStorage, and service workers that serve stale deployments.

The trade-off is convenience versus control — pick the mechanism that matches your coupling and performance budget.

Checklist:

• Match API to lifetime, size, and security needs.
• Know async boundaries and cancellation.
• Plan worker and SW lifecycle explicitly.
• Use observers instead of scroll polling where possible.