coder-typescript-async-concurrency

<skill_overview> <purpose>Write reliable async code with clear error handling and bounded concurrency</purpose> <triggers> <trigger>Writing async functions or promise chains</trigger> <trigger>Parallelizing independent tasks</trigger> <trigger>Adding cancellation or timeouts</trigger> <trigger>Debugging unhandled rejections</trigger> </triggers> <sources> <source url="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise">MDN Promise Reference</source> <source url="https://nodejs.org/api/globals.html#class-abortcontroller">Node.js AbortController</source> </sources> </skill_overview> <async_await_rules> <rules> <rule>Use async/await end-to-end; avoid mixing with callbacks</rule> <rule>Return Promise from async functions, never void</rule> <rule>Do not ignore rejected promises; handle or propagate</rule> </rules> </async_await_rules> <promise_composition> <rules> <rule>Use Promise.all for independent work that must all succeed</rule> <rule>Use Promise.allSettled when partial failures are acceptable</rule> <rule>Use Promise.race or Promise.any for first-success strategies</rule> </rules> <example> <code> const results = await Promise.allSettled([ fetchProfile(userId), fetchOrders(userId) ]); </code> </example> </promise_composition> <error_handling> <rules> <rule>Wrap awaited operations in try/catch at boundaries</rule> <rule>Normalize errors to a consistent shape for callers</rule> <rule>Use unknown in catch and narrow explicitly</rule> </rules> </error_handling> <cancellation> <rules> <rule>Pass AbortSignal through async call chains</rule> <rule>Abort work on timeouts or user cancellation</rule> </rules> <example> <code> const controller = new AbortController(); const { signal } = controller;

const task = fetch(url, { signal }); controller.abort(); await task; </code> </example> </cancellation> <concurrency_limits> <rules> <rule>Bound concurrency for IO-heavy operations</rule> <rule>Queue excess tasks instead of spawning unbounded promises</rule> </rules> </concurrency_limits> <anti_patterns> <avoid name="serial_awaits">Awaiting independent tasks sequentially</avoid> <avoid name="floating_promises">Creating promises without awaiting or handling</avoid> <avoid name="unbounded_parallelism">Launching too many requests at once</avoid> </anti_patterns>