How do you handle errors in async code, and what is an unhandled rejection?

Quick answer

Use try/catch with async/await or .catch on promise chains. An unhandled rejection is a rejected promise with no handler.

In detail

A rejected promise is the async version of a thrown error. With async/await wrap awaits in try/catch; with chains always end in `.catch`. Forgetting both produces an 'unhandled promise rejection', which can crash Node and is a common production bug. Note `Promise.all` rejects on the first failure — use allSettled to see all.

async function safe() {
  try { return await fetch("/x").then(r => r.json()); }
  catch (e) { report(e); return null; }
}
fetch("/x").then(r => r.json()).catch(report); // never forget

Why interviewers ask this: Production-readiness signal.

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