Default Value

On final failure (business error, or timeout after retries are exhausted), providing defaultValue swallows the error and resolves the fallback instead.

const loader = new AsyncLoader(fetchUser, { defaultValue: defaultUser });

const user = await loader.get(); // on failure, resolves defaultUser instead of throwing

Notes

• Falsy values (0 / "" / null / false) are valid fallbacks when explicitly provided.
• Has no effect on manual abort() (still rejects with AbortError).
• The fallback is not written to the cache, so the next get() reloads to fetch the real value.

When the fallback triggers

Scenario	Triggers defaultValue?
Business error (after retries exhausted)	✅ Yes
Timeout (after retries exhausted)	✅ Yes
Manual abort()	❌ No (rejects with AbortError)

Relationship with onFulfilled

When the fallback triggers, onFulfilled is still called with the fallback as result — success and fallback share a unified "success" semantics for callers.