Export CacheItem and CacheLike types for TypeScript custom cache definitions

[Copilot]

TypeScript users need to manually copy internal type definitions to create custom caches because CacheItem and CacheLike are not exported.

Changes

• index.ts: Export CacheItem<ValueType> and CacheLike<KeyType, ValueType> types
• test-d/index.test-d.ts: Add type tests verifying exported types work with custom cache implementations

Usage

import memoize, { type CacheItem, type CacheLike } from 'memoize';

// Type cache values directly
const cache = new Map<string, CacheItem<number>>();

// Or implement custom cache with proper typing
const customCache: CacheLike<string, number> = {
  has: (key) => cache.has(key),
  get: (key) => cache.get(key),
  set: (key, value) => cache.set(key, value),
  delete: (key) => cache.delete(key),
  clear: () => cache.clear(),
};

const memoized = memoize(expensiveFunction, { cache: customCache });

Original prompt

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This section details on the original issue you should resolve

<issue_title>Defining custom cache in TypeScript</issue_title>
<issue_description>Neither CacheItem, nor CacheLike are exported.
So, in order to define a custom cache, I have to manually copy the types:

// https://github.com/sindresorhus/memoize/blob/4c2b35fad5841cea20274b461fe2528fa40a692d/index.ts#L12-L15
type CacheItem<ValueType> = {
	data: ValueType;
	maxAge: number;
};

const cacheMap = new Map<Key, CacheItem<Value>>();

or, a bit nicer:

// https://github.com/sindresorhus/memoize/blob/4c2b35fad5841cea20274b461fe2528fa40a692d/index.ts#L12C1-L23C3
type CacheItem<ValueType> = {
	data: ValueType;
	maxAge: number;
};

type CacheLike<KeyType, ValueType> = {
	has: (key: KeyType) => boolean;
	get: (key: KeyType) => CacheItem<ValueType> | undefined;
	set: (key: KeyType, value: CacheItem<ValueType>) => void;
	delete: (key: KeyType) => void;
	clear?: () => void;
};

const cacheMap: CacheLike<Key, Value> = new Map();

Could we have some exported types?</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Defining custom cache in TypeScript #111

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[fregante]

@Richienb this?

[Richienb]

@fregante Yes, exporting the types is enough.

So it depends whether would be a good design decision to only export one of them (CacheLike), rather than both.

[sindresorhus]

These changes are not needed. We don't need tests to confirm that, yes, the two added export keywords do indeed work.