@monstermann/fn/dist/object/test.d.ts

A utility library for TypeScript.

import { AllUnionFields, Simplify } from "type-fest";

//#region src/object/test.d.ts
type Test<T extends object, U, V> = T extends unknown ? U extends keyof T ? V extends T[U] ? Simplify<T & Record<U, V>> : never : never : never;
/**
 * `test(target, key, predicate)`
 *
 * Checks if the `key` property of `target` object passes the `predicate` function test.
 *
 * ```ts
 * test({ a: 5, b: 2 }, "a", (x) => x > 3); // true
 * test({ a: 1, b: 2 }, "a", (x) => x > 3); // false
 * ```
 *
 * ```ts
 * pipe(
 *     { a: 5, b: 2 },
 *     test("a", (x) => x > 3),
 * ); // true
 *
 * pipe(
 *     { a: 1, b: 2 },
 *     test("a", (x) => x > 3),
 * ); // false
 * ```
 */
declare const test: {
  <T extends object, U extends keyof AllUnionFields<T>, V extends AllUnionFields<T>[U]>(key: U, predicate: (value: AllUnionFields<T>[U]) => value is V): (target: T) => target is Test<T, U, V>;
  <T extends object, U extends keyof AllUnionFields<T>>(key: U, predicate: (value: AllUnionFields<T>[U]) => boolean): (target: T) => target is Test<T, U, AllUnionFields<T>[U]>;
  <T extends object, U extends keyof AllUnionFields<T>, V extends AllUnionFields<T>[U]>(target: T, key: U, predicate: (value: AllUnionFields<T>[U]) => value is V): target is Test<T, U, V>;
  <T extends object, U extends keyof AllUnionFields<T>>(target: T, key: U, predicate: (value: AllUnionFields<T>[U]) => boolean): target is Test<T, U, AllUnionFields<T>[U]>;
};
//#endregion
export { test };