Cache

import Cache from '@bbc/front-end-kit/js/managers/Cache';

A generic in-memory cache manager for both synchronous and async (Promise-based) results. Runs a method once and reuses the result until the cache entry expires. Useful for avoiding redundant API calls or expensive computations within a session.

Getting started

import Cache from '@bbc/front-end-kit/js/managers/Cache';

const cache = new Cache();

// sync — method only runs once per key until expiration
const result = cache.runCached('my-key', () => expensiveComputation());

// async — promise only runs once per key until expiration
const data = await cache.runCachedPromise('my-api-call', () => fetch('/api/data').then(r => r.json()));

API

constructor(args = {})

Initialises the Cache instance with an empty internal Map.

Methods

runCached(key, method, options = {})

Runs method() and caches the result under key. On subsequent calls with the same key, returns the cached result until it expires — then re-runs method().

Parameters

• key (string): The cache key.
• method (Function): A function returning the value to cache.
• options (object, optional):
  • expiration (number, default 60000): Time in ms before the cached result is considered stale.

Returns

The return value of method(), or the previously cached result.

runCachedPromise(key, method, options = {})

Same as runCached but for Promise-returning methods. While the Promise is still pending, subsequent calls return the same in-flight Promise. Once resolved, the result is deep-cloned before returning to prevent external mutation of the cached value.

Parameters

• key (string): The cache key.
• method (Function): A function returning a Promise.
• options (object, optional):
  • expiration (number, default 60000): Time in ms before the cached result is considered stale.

Returns

Promise — resolves with a deep clone of the method's resolved value.

External dependencies

• lodash:
  • cloneDeep: Deep-clones resolved promise results to prevent external mutation.
  • defaultsDeep: Merges caller options over the default expiration.