Modern Async JavaScript Patterns (without the chaos)

Why async gets messy

Async/await hides the promise syntax but not the mental model. Bugs come from unbounded concurrency, unhandled rejections, and race conditions.

• Unbounded loops over async calls overwhelm APIs
• Mixed promise chains and async/await make stack traces harder
• Races happen when you assume order without awaiting all tasks

Control concurrency with pools

Batch work instead of firing everything at once. A simple concurrency pool keeps APIs happy and UIs responsive.

• Chunk arrays and await Promise.all per chunk
• Use a semaphore when tasks are dynamic
• Always add timeouts for remote calls

Cancellation and cleanup

AbortController is supported almost everywhere. Pass the signal to fetch or libraries that support it. Always clean up listeners on cancellation.

Error handling patterns

Prefer try/catch close to the await. For parallel tasks, collect results with Promise.allSettled and decide how to degrade gracefully.