froebel/memoize.d.ts

TypeScript utility library

import type { λ } from "./types";
/**
 * Returns a copy of `fun` that remembers its result for any given arguments and
 * only invokes `fun` for unknown arguments.
 *
 * The cache key is computed using the `key` function. The default `key`
 * function simply stringifies the arguments.
 *
 * If `limit` is specified, only the `limit`-last entries are kept in cache.
 *
 * The function's cache is available at `memoized.cache`.
 *
 * If `opt.weak` is `true`, non-primitive cache keys are stored in a WeakMap.
 * This behavior might for example be useful if you want to memoize some
 * calculation including a DOM Node without holding on to a reference of that
 * node.
 * Using weak keys prohibits setting a `limit`.
 *
 * @param fun - The function to be memoized.
 * @param opt - Optional additional parameters.
 * @returns The memoized function.
 *
 * @example
 * ```
 * const expensiveCalculation = (a: number, b: number) => {
 *   console.log(`calculate ${a} + ${b}`)
 *   return a + b
 * }
 * const calc = memoize(expensiveCalculation)
 *
 * console.log( calc(1, 2) )
 * // calculate 1 + 2
 * // 3
 * console.log( calc(20, 5) )
 * // calculate 20 + 5
 * // 25
 * console.log( calc(20, 5) )
 * // 25
 * console.log( calc(1, 2) )
 * // 3
 *
 * calc.cache.clear()
 * console.log( calc(1, 2) )
 * // calculate 1 + 2
 * // 3
 * ```
 *
 * @example
 * ```
 * const logIfDifferent = memoize(
 *   (msg: string) => console.log(msg),
 *   {
 *     limit: 1,
 *     key: msg => msg
 *   }
 * )
 *
 * logIfDifferent('a')
 * logIfDifferent('a')
 * logIfDifferent('b')
 * logIfDifferent('a')
 *
 * // a
 * // b
 * // a
 * ```
 */
declare const memoize: <T extends λ<any[], any>, K = string, W extends boolean = false>(fun: T, opt?: {
    /**
     * How the cache key is computed. Defaults to `JSON.stringify`ing the arguments.
     */
    key?: ((...args: Parameters<T>) => K) | undefined;
    /**
     * The maximum number of results that can be kept in cache before discarding the oldest result.
     */
    limit?: number | undefined;
    /**
     * Store non-primitive cache keys in a WeakMap.
     */
    weak?: W | undefined;
}) => T & {
    cache: W extends false ? Map<K, ReturnType<T>> : Cache<K, ReturnType<T>>;
};
export default memoize;
declare class Cache<K, V> {
    #private;
    delete(key: K): boolean;
    has(key: K): boolean;
    get(key: K): V | undefined;
    set(key: K, value: V): void;
}