Async Traps

Event Loop

• setImmediate runs after I/O — process.nextTick runs before (order matters)
• Long loops starve I/O — break with setImmediate every N iterations

Promises

• Promise.all() fails fast — one rejection kills all, use allSettled for partial results
• Forgetting await — function continues without waiting, no error thrown
• return await redundant — except inside try/catch (needed to catch rejection)
• Sequential await in loop is slow — use Promise.all(items.map(...)) for parallel

Callbacks

• Callback errors don't propagate — try/catch won't catch them, handle in callback
• Zalgo: mixing sync/async — always be consistent, async callback even for cached values