hp24-idemkit-client

Universal (browser + Node) idempotent fetch wrapper — the client half of idemkit. Zero dependencies.

npm install hp24-idemkit-client

It generates a stable Idempotency-Key per logical request, reuses the same key across retries, persists keys across interruptions (optional), and backs off between attempts. Pair it with an idemkit server adapter and a retried request replays instead of executing twice.

Usage

import { createIdempotentFetch } from 'hp24-idemkit-client';

const ifetch = createIdempotentFetch({
  retry: { retries: 3, minDelayMs: 200 },
});

const res = await ifetch('/api/charges', {
  method: 'POST',
  headers: { 'content-type': 'application/json' },
  body: JSON.stringify({ amount: 1000 }),
});

• A key is attached to mutating methods (POST/PUT/PATCH/DELETE) only.
• Network errors, 5xx, and 429 are retried (configurable via retryOn); Retry-After is honored.
• Every retry sends the same key, so the server deduplicates.

Surviving reloads

Persist the key so an operation interrupted mid-flight (tab reload, crash) retries with the same key:

import { createIdempotentFetch, localStorageKeyStore } from 'hp24-idemkit-client';

const ifetch = createIdempotentFetch({ keyStore: localStorageKeyStore() });

await ifetch('/api/orders', {
  method: 'POST',
  idempotencyId: 'checkout-cart-42', // stable id → stable key until it succeeds
  body: JSON.stringify(cart),
});

memoryKeyStore() (default-friendly) and localStorageKeyStore() are included; implement KeyStore for anything else.

License

MIT