Async States & Debounce

What you build

• Declare RequestState<T> as a discriminated union
• describe(state) returns a sentence for every status
• load(fetcher) resolves to a success or error state — it never throws
• debounce(fn, wait) delays the call
• A burst of calls results in exactly one invocation

Done means

Every state is handled, a rejected fetch becomes an error state, and three rapid calls fire once.

How it is graded

Published in full, before you start — every point is one of these and there is nothing else. Each one runs your code; it is not a search for keywords.

1. RequestState is a discriminated union of four states+15Union types and narrowing
2. describe handles every state+20Union types and narrowing
3. load resolves to a success state+20Async and its failure modes
4. A rejected fetch becomes an error state, not a throw+20Async and its failure modes
5. debounce waits before it calls+15Debouncing and throttling
6. A burst of calls fires exactly once+10Debouncing and throttling

What it teaches

The rest of JavaScript + TypeScript