# API Reference [← Back to README](../README.md) · [Documentation index](./README.md) ## Core API Overview **Main functions:** - **`createFetch(cache?, options?)`** - Cached fetch for outbound HTTP requests - **`createCacheHandler(cache, defaults?)`** - Cached resolver for in-process origin handlers - **`resolveWithCache(cache, request, origin, options?)`** - Low-level cache resolution (used by both APIs above) - **`createLogger(logger?, logLevel?, prefix?)`** - Create logger with level filtering **Classes:** - **`Cache`** - Main cache implementation - **`CacheStorage`** - Cache storage manager **Key types:** - **`KVStorage`** - Storage backend interface - **`SharedCacheRequestInitProperties`** - Request cache configuration - **`CacheKeyRules`** - Cache key generation rules --- ## createFetch Function Creates a fetch function with shared cache configuration. ```typescript function createFetch( cache?: Cache, options?: { fetch?: typeof fetch; defaults?: Partial<sharedcacherequestinitproperties>; } ): SharedCacheFetch; ``` **Parameters:** - **`cache`** - Optional SharedCache instance (auto-discovered from globalThis.caches if not provided) - **`options.fetch`** - Custom fetch implementation to use as the underlying fetcher (defaults to globalThis.fetch) - **`options.defaults`** - Default shared cache options to apply to all requests **Returns:** `SharedCacheFetch` - A fetch function with caching capabilities **Basic usage:** ```typescript const cache = await caches.open('my-cache'); const fetch = createFetch(cache, { defaults: { cacheControlOverride: 's-maxage=300' }, }); ``` ## createCacheHandler / resolveWithCache For in-process origins (e.g. middleware `next()`). Same cache options as `createFetch`. On cache miss, origin throws propagate; during revalidation, throws become 5xx for `stale-if-error`. ```typescript const handler = createCacheHandler(cache, { cacheControlOverride: 's-maxage=60', }); await handler.resolve(request, () => next(), { waitUntil }); ``` Use `createFetch` for outbound HTTP; use `createCacheHandler` for in-process handlers. ## Key Interfaces ### SharedCacheRequestInitProperties Request-level cache configuration: ```typescript interface SharedCacheRequestInitProperties { cacheControlOverride?: string; cacheKeyRules?: CacheKeyRules; ignoreRequestCacheControl?: boolean; ignoreVary?: boolean; varyOverride?: string; event?: ExtendableEvent; } ``` ### CacheKeyRules Cache key generation rules: ```typescript interface CacheKeyRules { cookie?: KeyFilterOptions | boolean; device?: KeyFilterOptions | boolean; header?: KeyFilterOptions | boolean; search?: KeyFilterOptions | boolean; } ``` ### KVStorage Storage backend interface: ```typescript interface KVStorage { get: (cacheKey: string) => Promise<unknown | undefined>; set: (cacheKey: string, value: unknown, ttl?: number) => Promise<void>; delete: (cacheKey: string) => Promise<boolean>; } ``` ## Classes ### Cache / CacheStorage ```typescript class Cache { match(request: RequestInfo | URL): Promise<response | undefined>; put(request: RequestInfo | URL, response: Response): Promise<void>; delete(request: RequestInfo | URL): Promise<boolean>; } class CacheStorage { constructor(storage: KVStorage); open(cacheName: string): Promise<cache>; } ``` ## Utilities ### `createLogger(logger?, logLevel?, prefix?)` ```typescript const logger = createLogger(console, LogLevel.INFO, 'MyApp'); ``` Creates a structured logger with level filtering and optional prefix. ### Cache Status Values ```typescript type CacheStatus = | 'HIT' | 'MISS' | 'EXPIRED' | 'UPDATING' | 'STALE' | 'BYPASS' | 'REVALIDATED' | 'DYNAMIC'; ``` Status values are automatically added to response headers as `x-cache-status`. **Complete API documentation** is also available in TypeScript definitions and source code.