declare type AnyFunction = (...arguments_: any) => any; interface CacheStorageContent { data: ValueType; maxAge: number; } interface CacheStorage { has: (key: KeyType) => boolean; get: (key: KeyType) => CacheStorageContent | undefined; set: (key: KeyType, value: CacheStorageContent) => void; delete: (key: KeyType) => void; clear?: () => void; } interface Options { /** Milliseconds until the cache expires. @default Infinity */ readonly maxAge?: number; /** Determines the cache key for storing the result based on the function arguments. By default, __only the first argument is considered__ and it only works with [primitives](https://developer.mozilla.org/en-US/docs/Glossary/Primitive). A `cacheKey` function can return any type supported by `Map` (or whatever structure you use in the `cache` option). You can have it cache **all** the arguments by value with `JSON.stringify`, if they are compatible: ``` import mem = require('mem'); mem(function_, {cacheKey: JSON.stringify}); ``` Or you can use a more full-featured serializer like [serialize-javascript](https://github.com/yahoo/serialize-javascript) to add support for `RegExp`, `Date` and so on. ``` import mem = require('mem'); import serializeJavascript = require('serialize-javascript'); mem(function_, {cacheKey: serializeJavascript}); ``` @default arguments_ => arguments_[0] @example arguments_ => JSON.stringify(arguments_) */ readonly cacheKey?: (arguments_: Parameters) => CacheKeyType; /** Use a different cache storage. Must implement the following methods: `.has(key)`, `.get(key)`, `.set(key, value)`, `.delete(key)`, and optionally `.clear()`. You could for example use a `WeakMap` instead or [`quick-lru`](https://github.com/sindresorhus/quick-lru) for a LRU cache. @default new Map() @example new WeakMap() */ readonly cache?: CacheStorage>; } /** [Memoize](https://en.wikipedia.org/wiki/Memoization) functions - An optimization used to speed up consecutive function calls by caching the result of calls with identical input. @param fn - Function to be memoized. @example ``` import mem = require('mem'); let i = 0; const counter = () => ++i; const memoized = mem(counter); memoized('foo'); //=> 1 // Cached as it's the same arguments memoized('foo'); //=> 1 // Not cached anymore as the arguments changed memoized('bar'); //=> 2 memoized('bar'); //=> 2 ``` */ declare const mem: { (fn: FunctionToMemoize, { cacheKey, cache, maxAge }?: Options): FunctionToMemoize; /** @returns A [decorator](https://github.com/tc39/proposal-decorators) to memoize class methods or static class methods. @example ``` import mem = require('mem'); class Example { index = 0 @mem.decorator() counter() { return ++this.index; } } class ExampleWithOptions { index = 0 @mem.decorator({maxAge: 1000}) counter() { return ++this.index; } } ``` */ decorator(options?: Options): (target: any, propertyKey: string, descriptor: PropertyDescriptor) => void; /** Clear all cached data of a memoized function. @param fn - Memoized function. */ clear(fn: AnyFunction): void; }; export = mem;