ts-vista/dist/index.d.ts

An utility to enhance TypeScript

/**
 * Construct a type with the properties of T
 * except for those in type K.
 *
 * ### Example
 *
 * ```ts
 * import type { Omit } from "ts-vista";
 *
 * type T = {
 *   a: string;
 *   b: number;
 *   c: boolean;
 * };
 *
 * // D1 = { b: number; c: boolean; }
 * type D1 = Omit<T, "a">;
 *
 * // D2 = { c: boolean; }
 * type D2 = Omit<T, "a" | "b">;
 * ```
 */
type Omit<T, K extends keyof T> = {
    [KY in keyof T as KY extends K ? never : KY]: T[KY];
};

/**
 * Make properties in T readonly.
 *
 * ### Example
 *
 * ```ts
 * import type { Readonly } from "ts-vista";
 *
 * type T = {
 *     a: string;
 *     b: number;
 *     c: boolean;
 * };
 *
 * // C1 = {
 * //     readonly a: string;
 * //     readonly b: number;
 * //     readonly c: boolean;
 * // }
 * type C1 = Readonly<T>;
 *
 * // C2 = { readonly a: string; b: number; c: boolean; }
 * type C2 = Readonly<T, "a">;
 *
 * // C3 = { readonly a: string; readonly b: number; c: boolean; }
 * type C3 = Readonly<T, "a" | "b">;
 * ```
 */
type _Readonly<T, K extends keyof T = keyof T> = Omit<T, K> & Readonly<Pick<T, K>>;

/**
 * Make properties in T optional.
 *
 * ### Example
 *
 * ```ts
 * import type { Partial } from "ts-vista";
 *
 * type T = {
 *     a: string;
 *     b: number;
 *     c: boolean;
 * };
 *
 * // O1 = { a?: string; b?: number; c?: boolean; }
 * type O1 = Partial<T>;
 *
 * // O2 = { a?: string; b: number; c: boolean; }
 * type O2 = Partial<T, "a">;
 *
 * // O3 = { a?: string; b?: number; c: boolean; }
 * type O3 = Partial<T, "a" | "b">;
 * ```
 */
type _Partial<T, K extends keyof T = keyof T> = Omit<T, K> & Partial<Pick<T, K>>;

/**
 * Extract from T those types that are assignable to U.
 *
 * ### Example
 *
 * ```ts
 * import type { Extract } from "ts-vista";
 *
 * type T1 = {
 *   type: "a";
 *   name: string;
 * };
 *
 * type T2 = {
 *   type: "b";
 *   age: number;
 * };
 *
 * type T3 = {
 *   type: "c";
 *   color: string;
 * };
 *
 * type T4 = T1 | T2 | T3;
 *
 * // P1X = T1
 * type P1A = Extract<T4, T1>;
 * type P1B = Extract<T4, { type: "a" }>;
 *
 * // P2X = T1 | T2
 * type P2A = Extract<T4, T1 | T2>;
 * type P2B = Extract<T4, { type: "a" } | { type: "b" }>;
 * ```
 */
type Extract<T, U extends Partial<T>> = T extends U ? T : never;

/**
 * Exclude from T those types that are assignable to U.
 *
 * ### Example
 *
 * ```ts
 * import type { Exclude } from "ts-vista";
 *
 * type T1 = {
 *   type: "a";
 *   name: string;
 * };
 *
 * type T2 = {
 *   type: "b";
 *   age: number;
 * };
 *
 * type T3 = {
 *   type: "c";
 *   color: string;
 * };
 *
 * type T4 = T1 | T2 | T3;
 *
 * // D1X = T2 | T3
 * type D1A = Exclude<T4, T1>;
 * type D1B = Exclude<T4, { type: "a"; name: string }>;
 *
 * // D2X = T3
 * type D2A = Exclude<T4, T1 | T2>;
 * type D2B = Exclude<
 *     T4,
 *     | { type: "a"; name: string }
 *     | { type: "b"; age: number }
 * >;
 * ```
 */
type Exclude<T, U extends T> = T extends U ? never : T;

/**
 * Make all properties in T visible.
 *
 * ### Example
 *
 * ```ts
 * import type { Format } from "ts-vista";
 *
 * type T1 = {
 *   a: string;
 *   b: number;
 * };
 *
 * type T2 = {
 *   c: string;
 *   d: number;
 * };
 *
 * // F = { a: string; b: number; c: string; d: number; }
 * type F = Format<T1 & T2>;
 * ```
 */
type Format<T> = T extends Function ? T : {
    [K in keyof T]: T[K];
};

/**
 * From `object`, pick a set of properties whose keys are in `keys`.
 *
 * ### Example
 *
 * ```ts
 * import { pick } from "ts-vista";
 *
 * type Keys = {
 *     a: number;
 *     b: number;
 *     c: number;
 * };
 *
 * type Keys2 = Pick<Keys, "a" | "b">;
 *
 * const keys: Keys = {
 *     a: 1,
 *     b: 2,
 *     c: 3,
 * };
 *
 * const keys2: Keys2 = pick(keys, ["a", "b"]);
 * ```
 */
declare const pick: <T extends object, K extends (keyof T)[]>(object: T, keys: K) => Pick<T, K[number]>;

/**
 * Construct an object with the properties of `object`
 * except for those in `keys`.
 *
 * ### Example
 *
 * ```ts
 * import type { Omit } from "ts-vista";
 *
 * import { omit } from "ts-vista";
 *
 * type Keys = {
 *     a: number;
 *     b: number;
 *     c: number;
 * };
 *
 * type Keys2 = Omit<Keys, "a" | "b">;
 *
 * const keys: Keys = {
 *     a: 1,
 *     b: 2,
 *     c: 3,
 * };
 *
 * const keys2: Keys2 = omit(keys, ["a", "b"]);
 * ```
 */
declare const omit: <T extends object, K extends (keyof T)[]>(object: T, keys: K) => Omit<T, K[number]>;

export { type Exclude, type Extract, type Format, type Omit, type _Partial as Partial, type _Readonly as Readonly, omit, pick };