declare type AnyFunction = (...arguments_: any) => any;
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interface CacheStorageContent<ValueType> {
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data: ValueType;
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maxAge: number;
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}
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interface CacheStorage<KeyType, ValueType> {
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has: (key: KeyType) => boolean;
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get: (key: KeyType) => CacheStorageContent<ValueType> | undefined;
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set: (key: KeyType, value: CacheStorageContent<ValueType>) => void;
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delete: (key: KeyType) => void;
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clear?: () => void;
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}
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interface Options<FunctionToMemoize extends AnyFunction, CacheKeyType> {
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/**
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Milliseconds until the cache expires.
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@default Infinity
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*/
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readonly maxAge?: number;
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/**
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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).
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A `cacheKey` function can return any type supported by `Map` (or whatever structure you use in the `cache` option).
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You can have it cache **all** the arguments by value with `JSON.stringify`, if they are compatible:
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```
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import mem = require('mem');
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mem(function_, {cacheKey: JSON.stringify});
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```
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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.
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```
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import mem = require('mem');
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import serializeJavascript = require('serialize-javascript');
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mem(function_, {cacheKey: serializeJavascript});
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```
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@default arguments_ => arguments_[0]
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@example arguments_ => JSON.stringify(arguments_)
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*/
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readonly cacheKey?: (arguments_: Parameters<FunctionToMemoize>) => CacheKeyType;
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/**
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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.
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@default new Map()
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@example new WeakMap()
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*/
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readonly cache?: CacheStorage<CacheKeyType, ReturnType<FunctionToMemoize>>;
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}
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/**
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[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.
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@param fn - Function to be memoized.
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@example
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```
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import mem = require('mem');
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let i = 0;
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const counter = () => ++i;
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const memoized = mem(counter);
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memoized('foo');
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//=> 1
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// Cached as it's the same arguments
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memoized('foo');
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//=> 1
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// Not cached anymore as the arguments changed
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memoized('bar');
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//=> 2
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memoized('bar');
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//=> 2
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```
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*/
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declare const mem: {
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<FunctionToMemoize extends AnyFunction, CacheKeyType>(fn: FunctionToMemoize, { cacheKey, cache, maxAge }?: Options<FunctionToMemoize, CacheKeyType>): FunctionToMemoize;
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/**
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@returns A [decorator](https://github.com/tc39/proposal-decorators) to memoize class methods or static class methods.
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@example
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```
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import mem = require('mem');
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class Example {
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index = 0
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@mem.decorator()
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counter() {
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return ++this.index;
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}
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}
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class ExampleWithOptions {
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index = 0
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@mem.decorator({maxAge: 1000})
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counter() {
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return ++this.index;
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}
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}
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```
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*/
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decorator<FunctionToMemoize_1 extends AnyFunction, CacheKeyType_1>(options?: Options<FunctionToMemoize_1, CacheKeyType_1>): (target: any, propertyKey: string, descriptor: PropertyDescriptor) => void;
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/**
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Clear all cached data of a memoized function.
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@param fn - Memoized function.
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*/
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clear(fn: AnyFunction): void;
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};
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export = mem;
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