@monstermann/fn/dist/option/filter.d.ts

A utility library for TypeScript.

import { NonNil } from "../internals/types.js";

//#region src/option/filter.d.ts

/**
 * `filter(target, predicate)`
 *
 * Filters a value based on a predicate function. If the value is `null` or `undefined`, it returns the value unchanged. If the value satisfies the predicate, it returns the value. Otherwise, it returns `undefined`.
 *
 * ```ts
 * filter(5, (x) => x > 3); // 5
 * filter(2, (x) => x > 3); // undefined
 * filter(null, (x) => x > 3); // null
 * filter(undefined, (x) => x > 3); // undefined
 * ```
 *
 * ```ts
 * pipe(
 *     5,
 *     filter((x) => x > 3),
 * ); // 5
 *
 * pipe(
 *     2,
 *     filter((x) => x > 3),
 * ); // undefined
 * ```
 */
declare const filter: {
  <T, U extends NonNil<T>>(predicate: (value: NoInfer<NonNil<T>>) => value is U): (target: T) => U | undefined;
  <T>(predicate: (value: NoInfer<NonNil<T>>) => boolean): (target: T) => T | undefined;
  <T, U extends NonNil<T>>(target: T, predicate: (value: NoInfer<NonNil<T>>) => value is U): U | undefined;
  <T>(target: T, predicate: (value: NoInfer<NonNil<T>>) => boolean): T | undefined;
};
//#endregion
export { filter };