...

utility-types

Collection of utility types, complementing TypeScript built-in mapped types and aliases (think "lodash" for static types).
GitHub
5.54k
Created 8 years ago, last commit 4 months ago
30 contributors
250 commits
Stars added on GitHub, month by month
11
12
1
2
3
4
5
6
7
8
9
10
2023
2024
Stars added on GitHub, per day, on average
Yesterday
+2
Last week
+1.0
/day
Last month
+0.7
/day
Last 12 months
+1.1
/day
Package on NPM
utility-types
3.11.0
Monthly downloads on NPM
11
12
1
2
3
4
5
6
7
8
9
10
2023
2024
No dependencies
README

utility-types

Collection of utility types, complementing TypeScript built-in mapped types and aliases (think "lodash" for static types).

Latest Stable Version NPM Downloads NPM Downloads Bundlephobia Size

CI Check License Join the community on Spectrum

Found it useful? Want more updates?

Show your support by giving a ⭐

Buy Me a Coffee Become a Patron


What's new?

🎉 Added new utilities 🎉


Features

Goals

  • Quality - thoroughly tested for type correctness with type-testing library dts-jest
  • Secure and minimal - no third-party dependencies
  • No runtime cost - it's type-level only

Installation

# NPM
npm install utility-types

# YARN
yarn add utility-types

Compatibility Notes

TypeScript support

  • v3.x.x - TypeScript v3.1+
  • v2.x.x - TypeScript v2.8.1+
  • v1.x.x - TypeScript v2.7.2+

Funding Issues

Utility-Types is an open-source project created by people investing their time for the benefit of our community.

Issues like bug fixes or feature requests can be very quickly resolved when funded through the IssueHunt platform.

I highly recommend adding a bounty to the issue that you're waiting for to attract some contributors willing to work on it.

Let's fund issues in this repository

Contributing

We are open for contributions. If you're planning to contribute please make sure to read the contributing guide as it can save you from wasting your time: CONTRIBUTING.md

  • (built-in) - types built-in TypeScript, no need to import

Table of Contents

Aliases & Type Guards

Union operators

Object operators

Special operators

Flow's Utility Types

Deprecated API (use at own risk)

  • getReturnOfExpression() - from TS v2.0 it's better to use type-level ReturnType instead

Primitive

Type representing primitive types in JavaScript, and thus TypeScript: string | number | bigint | boolean | symbol | null | undefined

You can test for singular of these types with typeof

isPrimitive

This is a TypeScript Typeguard for the Primitive type.

This can be useful to control the type of a parameter as the program flows. Example:

const consumer = (param: Primitive[] | Primitive): string => {
    if (isPrimitive(param)) {
        // typeof param === Primitive
        return String(param) + ' was Primitive';
    }
    // typeof param === Primitive[]
    const resultArray = param
        .map(consumer)
        .map(rootString => '\n\t' + rootString);
    return resultArray.reduce((comm, newV) => comm + newV, 'this was nested:');
};

⇧ back to top

Falsy

Type representing falsy values in TypeScript: false | "" | 0 | null | undefined

Except NaN which cannot be represented as a type literal

isFalsy

const consumer = (param: Falsy | string): string => {
    if (isFalsy(param)) {
        // typeof param === Falsy
        return String(param) + ' was Falsy';
    }
    // typeof param === string
    return param.toString();
};

⇧ back to top

Nullish

Type representing nullish values in TypeScript: null | undefined

⇧ back to top

isNullish

const consumer = (param: Nullish | string): string => {
    if (isNullish(param)) {
        // typeof param === Nullish
        return String(param) + ' was Nullish';
    }
    // typeof param === string
    return param.toString();
};

⇧ back to top

SetIntersection<A, B> (same as Extract)

Set intersection of given union types A and B

Usage:

import { SetIntersection } from 'utility-types';

// Expect: "2" | "3"
type ResultSet = SetIntersection<'1' | '2' | '3', '2' | '3' | '4'>;
// Expect: () => void
type ResultSetMixed = SetIntersection<string | number | (() => void), Function>;

⇧ back to top

SetDifference<A, B> (same as Exclude)

Set difference of given union types A and B

Usage:

import { SetDifference } from 'utility-types';

// Expect: "1"
type ResultSet = SetDifference<'1' | '2' | '3', '2' | '3' | '4'>;
// Expect: string | number
type ResultSetMixed = SetDifference<string | number | (() => void), Function>;

⇧ back to top

SetComplement<A, A1>

Set complement of given union types A and (it's subset) A1

Usage:

import { SetComplement } from 'utility-types';

// Expect: "1"
type ResultSet = SetComplement<'1' | '2' | '3', '2' | '3'>;

⇧ back to top

SymmetricDifference<A, B>

Set difference of union and intersection of given union types A and B

Usage:

import { SymmetricDifference } from 'utility-types';

// Expect: "1" | "4"
type ResultSet = SymmetricDifference<'1' | '2' | '3', '2' | '3' | '4'>;

⇧ back to top

NonNullable<A>

Exclude null and undefined from set A

⇧ back to top

NonUndefined<A>

Exclude undefined from set A

⇧ back to top

Exclude<A, B>

Exclude subset B from set A

⇧ back to top

Extract<A, B>

Extract subset B from set A

⇧ back to top

Operations on objects

FunctionKeys<T>

Get union type of keys that are functions in object type T

Usage:

import { FunctionKeys } from 'utility-types';

type MixedProps = { name: string; setName: (name: string) => void };

// Expect: "setName"
type Keys = FunctionKeys<MixedProps>;

⇧ back to top

NonFunctionKeys<T>

Get union type of keys that are non-functions in object type T

Usage:

import { NonFunctionKeys } from 'utility-types';

type MixedProps = { name: string; setName: (name: string) => void };

// Expect: "name"
type Keys = NonFunctionKeys<MixedProps>;

⇧ back to top

MutableKeys<T>

Get union type of keys that are mutable (not readonly) in object type T

Alias: WritableKeys<T>

Usage:

import { MutableKeys } from 'utility-types';

type Props = { readonly foo: string; bar: number };

// Expect: "bar"
type Keys = MutableKeys<Props>;

⇧ back to top

ReadonlyKeys<T>

Get union type of keys that are readonly in object type T

Usage:

import { ReadonlyKeys } from 'utility-types';

type Props = { readonly foo: string; bar: number };

// Expect: "foo"
type Keys = ReadonlyKeys<Props>;

⇧ back to top

RequiredKeys<T>

Get union type of keys that are required in object type T

Usage:

import { RequiredKeys } from 'utility-types';

type Props = { req: number; reqUndef: number | undefined; opt?: string; optUndef?: number | undefined; };

// Expect: "req" | "reqUndef"
type Keys = RequiredKeys<Props>;

⇧ back to top

OptionalKeys<T>

Get union type of keys that are optional in object type T

Usage:

import { OptionalKeys } from 'utility-types';

type Props = { req: number; reqUndef: number | undefined; opt?: string; optUndef?: number | undefined; };

// Expect: "opt" | "optUndef"
type Keys = OptionalKeys<Props>;

⇧ back to top

UnionKeys<U>

Get keys of all objects in the union type U

Usage:

import { UnionKeys } from 'utility-types';

type Props = { name: string } | { age: number } | { visible: boolean };

// Expect: "name" | "age" | "visible"
type Keys = UnionKeys<Props>;

⇧ back to top

Optional<T, K>

From T make a set of properties by key K become optional

Usage:

import { Optional } from 'utility-types';

type Props = { name: string; age: number; visible: boolean; };

// Expect: { name?: string; age?: number; visible?: boolean; }
type Props = Optional<Props>
// Expect: { name: string; age?: number; visible?: boolean; }
type Props = Optional<Props, 'age' | 'visible'>;

⇧ back to top

Pick<T, K> (built-in)

From T pick a set of properties by key K

Usage:

type Props = { name: string; age: number; visible: boolean };

// Expect: { age: number; }
type Props = Pick<Props, 'age'>;

⇧ back to top

PickByValue<T, ValueType>

From T pick a set of properties by value matching ValueType. (Credit: Piotr Lewandowski)

Usage:

import { PickByValue } from 'utility-types';

type Props = { req: number; reqUndef: number | undefined; opt?: string; };

// Expect: { req: number }
type Props = PickByValue<Props, number>;
// Expect: { req: number; reqUndef: number | undefined; }
type Props = PickByValue<Props, number | undefined>;

⇧ back to top

PickByValueExact<T, ValueType>

From T pick a set of properties by value matching exact ValueType.

Usage:

import { PickByValueExact } from 'utility-types';

type Props = { req: number; reqUndef: number | undefined; opt?: string; };

// Expect: { req: number }
type Props = PickByValueExact<Props, number>;
// Expect: { reqUndef: number | undefined; }
type Props = PickByValueExact<Props, number | undefined>;

⇧ back to top

Omit<T, K>

From T remove a set of properties by key K

Usage:

import { Omit } from 'utility-types';

type Props = { name: string; age: number; visible: boolean };

// Expect: { name: string; visible: boolean; }
type Props = Omit<Props, 'age'>;

⇧ back to top

OmitByValue<T, ValueType>

From T remove a set of properties by value matching ValueType. (Credit: Piotr Lewandowski)

Usage:

import { OmitByValue } from 'utility-types';

type Props = { req: number; reqUndef: number | undefined; opt?: string; };

// Expect: { reqUndef: number | undefined; opt?: string; }
type Props = OmitByValue<Props, number>;
// Expect: { opt?: string; }
type Props = OmitByValue<Props, number | undefined>;

⇧ back to top

OmitByValueExact<T, ValueType>

From T remove a set of properties by value matching exact ValueType.

Usage:

import { OmitByValueExact } from 'utility-types';

type Props = { req: number; reqUndef: number | undefined; opt?: string; };

// Expect: { reqUndef: number | undefined; opt?: string; }
type Props = OmitByValueExact<Props, number>;
// Expect: { req: number; opt?: string }
type Props = OmitByValueExact<Props, number | undefined>;

⇧ back to top

Intersection<T, U>

From T pick properties that exist in U

Usage:

import { Intersection } from 'utility-types';

type Props = { name: string; age: number; visible: boolean };
type DefaultProps = { age: number };

// Expect: { age: number; }
type DuplicatedProps = Intersection<Props, DefaultProps>;

⇧ back to top

Diff<T, U>

From T remove properties that exist in U

Usage:

import { Diff } from 'utility-types';

type Props = { name: string; age: number; visible: boolean };
type DefaultProps = { age: number };

// Expect: { name: string; visible: boolean; }
type RequiredProps = Diff<Props, DefaultProps>;

⇧ back to top

Subtract<T, T1>

From T remove properties that exist in T1 (T1 has a subset of the properties of T)

Usage:

import { Subtract } from 'utility-types';

type Props = { name: string; age: number; visible: boolean };
type DefaultProps = { age: number };

// Expect: { name: string; visible: boolean; }
type RequiredProps = Subtract<Props, DefaultProps>;

⇧ back to top

Overwrite<T, U>

From U overwrite properties to T

Usage:

import { Overwrite } from 'utility-types';

type Props = { name: string; age: number; visible: boolean };
type NewProps = { age: string; other: string };

// Expect: { name: string; age: string; visible: boolean; }
type ReplacedProps = Overwrite<Props, NewProps>;

⇧ back to top

Assign<T, U>

From U assign properties to T (just like object assign)

Usage:

import { Assign } from 'utility-types';

type Props = { name: string; age: number; visible: boolean };
type NewProps = { age: string; other: string };

// Expect: { name: string; age: string; visible: boolean; other: string; }
type ExtendedProps = Assign<Props, NewProps>;

⇧ back to top

ValuesType<T>

Get the union type of all the values in an object, tuple, array or array-like type T.

Usage:

import { ValuesType } from 'utility-types';

type Props = { name: string; age: number; visible: boolean };
// Expect: string | number | boolean
type PropsValues = ValuesType<Props>;

type NumberArray = number[];
// Expect: number
type NumberItems = ValuesType<NumberArray>;

type ReadonlyNumberTuple = readonly [1, 2];
// Expect: 1 | 2
type AnotherNumberUnion = ValuesType<NumberTuple>;

type BinaryArray = Uint8Array;
// Expect: number
type BinaryItems = ValuesType<BinaryArray>;

⇧ back to top

Partial<T>

Make all properties of object type optional

⇧ back to top

Required<T, K>

From T make a set of properties by key K become required

Usage:

import { Required } from 'utility-types';

type Props = { name?: string; age?: number; visible?: boolean; };

// Expect: { name: string; age: number; visible: boolean; }
type Props = Required<Props>
// Expect: { name?: string; age: number; visible: boolean; }
type Props = Required<Props, 'age' | 'visible'>;

⇧ back to top

Readonly<T>

Make all properties of object type readonly

⇧ back to top

Mutable<T>

From T make all properties become mutable

Alias: Writable<T>

import { Mutable } from 'utility-types';

type Props = {
  readonly name: string;
  readonly age: number;
  readonly visible: boolean;
};

// Expect: { name: string; age: number; visible: boolean; }
Mutable<Props>;

⇧ back to top

ReturnType<T>

Obtain the return type of a function

⇧ back to top

InstanceType<T>

Obtain the instance type of a class

⇧ back to top

Unionize<T>

Disjoin object to form union of objects, each with single property

Usage:

import { Unionize } from 'utility-types';

type Props = { name: string; age: number; visible: boolean };

// Expect: { name: string; } | { age: number; } | { visible: boolean; }
type UnionizedType = Unionize<Props>;

⇧ back to top

PromiseType<T>

Obtain Promise resolve type

Usage:

import { PromiseType } from 'utility-types';

// Expect: string
type Response = PromiseType<Promise<string>>;

⇧ back to top

DeepReadonly<T>

Readonly that works for deeply nested structures

Usage:

import { DeepReadonly } from 'utility-types';

type NestedProps = {
  first: {
    second: {
      name: string;
    };
  };
};

// Expect: {
//   readonly first: {
//     readonly second: {
//       readonly name: string;
//     };
//   };
// }
type ReadonlyNestedProps = DeepReadonly<NestedProps>;

⇧ back to top

DeepRequired<T>

Required that works for deeply nested structures

Usage:

import { DeepRequired } from 'utility-types';

type NestedProps = {
  first?: {
    second?: {
      name?: string;
    };
  };
};

// Expect: {
//   first: {
//     second: {
//       name: string;
//     };
//   };
// }
type RequiredNestedProps = DeepRequired<NestedProps>;

⇧ back to top

DeepNonNullable<T>

NonNullable that works for deeply nested structure

Usage:

import { DeepNonNullable } from 'utility-types';

type NestedProps = {
  first?: null | {
    second?: null | {
      name?: string | null | undefined;
    };
  };
};

// Expect: {
//   first: {
//     second: {
//       name: string;
//     };
//   };
// }
type RequiredNestedProps = DeepNonNullable<NestedProps>;

⇧ back to top

DeepPartial<T>

Partial that works for deeply nested structures

Usage:

import { DeepPartial } from 'utility-types';

type NestedProps = {
  first: {
    second: {
      name: string;
    };
  };
};

// Expect: {
//   first?: {
//     second?: {
//       name?: string;
//     };
//   };
// }
type PartialNestedProps = DeepPartial<NestedProps>;

⇧ back to top

Brand<T, U>

Define nominal type of U based on type of T. Similar to Opaque types in Flow.

Usage:

import { Brand } from 'utility-types';

type USD = Brand<number, "USD">
type EUR = Brand<number, "EUR">

const tax = 5 as USD;
const usd = 10 as USD;
const eur = 10 as EUR;

function gross(net: USD): USD {
  return (net + tax) as USD;
}

gross(usd); // ok
gross(eur); // Type '"EUR"' is not assignable to type '"USD"'.

⇧ back to top

UnionToIntersection<U>

Get intersection type given union type U

Usage:

import { UnionToIntersection } from 'utility-types';

// Expect: { name: string } & { age: number } & { visible: boolean }
UnionToIntersection<{ name: string } | { age: number } | { visible: boolean }>

⇧ back to top

Flow's Utility Types

$Keys<T>

get the union type of all the keys in an object type T
https://flow.org/en/docs/types/utilities/#toc-keys

Usage:

import { $Keys } from 'utility-types';

type Props = { name: string; age: number; visible: boolean };

// Expect: "name" | "age" | "visible"
type PropsKeys = $Keys<Props>;

⇧ back to top

$Values<T>

get the union type of all the values in an object type T
https://flow.org/en/docs/types/utilities/#toc-values

Usage:

import { $Values } from 'utility-types';

type Props = { name: string; age: number; visible: boolean };

// Expect: string | number | boolean
type PropsValues = $Values<Props>;

⇧ back to top

get the read-only version of a given object type T
https://flow.org/en/docs/types/utilities/#toc-readonly

Usage:

import { $ReadOnly } from 'utility-types';

type Props = { name: string; age: number; visible: boolean };

// Expect: Readonly<{ name: string; age: number; visible: boolean; }>
type ReadOnlyProps = $ReadOnly<Props>;

⇧ back to top

get the set difference of a given object types T and U (T \ U)
https://flow.org/en/docs/types/utilities/#toc-diff

Usage:

import { $Diff } from 'utility-types';

type Props = { name: string; age: number; visible: boolean };
type DefaultProps = { age: number };

// Expect: { name: string; visible: boolean; }
type RequiredProps = $Diff<Props, DefaultProps>;

⇧ back to top

$PropertyType<T, K>

get the type of property of an object at a given key K
https://flow.org/en/docs/types/utilities/#toc-propertytype

Usage:

import { $PropertyType } from 'utility-types';

type Props = { name: string; age: number; visible: boolean };
// Expect: string
type NameType = $PropertyType<Props, 'name'>;

type Tuple = [boolean, number];
// Expect: boolean
type A = $PropertyType<Tuple, '0'>;
// Expect: number
type B = $PropertyType<Tuple, '1'>;

⇧ back to top

$ElementType<T, K>

get the type of elements inside of array, tuple or object of type T, that matches the given index type K
https://flow.org/en/docs/types/utilities/#toc-elementtype

Usage:

import { $ElementType } from 'utility-types';

type Props = { name: string; age: number; visible: boolean };
// Expect: string
type NameType = $ElementType<Props, 'name'>;

type Tuple = [boolean, number];
// Expect: boolean
type A = $ElementType<Tuple, 0>;
// Expect: number
type B = $ElementType<Tuple, 1>;

type Arr = boolean[];
// Expect: boolean
type ItemsType = $ElementType<Arr, number>;

type Obj = { [key: string]: number };
// Expect: number
type ValuesType = $ElementType<Obj, string>;

⇧ back to top

$Call<T>

get the return type of a given expression type
https://flow.org/en/docs/types/utilities/#toc-call

The built-in ReturnType can be used to accomplish the same goal, although it may have some subtle differences.

Usage:

import { $Call } from 'utility-types';

// Common use-case
const add = (amount: number) => ({ type: 'ADD' as 'ADD', payload: amount });
type AddAction = $Call<typeof add>; // { type: 'ADD'; payload: number }

// Examples migrated from Flow docs
type ExtractPropType<T extends { prop: any }> = (arg: T) => T['prop'];
type Obj = { prop: number };
type PropType = $Call<ExtractPropType<Obj>>; // number
// type Nope = $Call<ExtractPropType<{ nope: number }>>; // Error: argument doesn't match `Obj`.

type ExtractReturnType<T extends () => any> = (arg: T) => ReturnType<T>;
type Fn = () => number;
type FnReturnType = $Call<ExtractReturnType<Fn>>; // number

⇧ back to top

$Shape<T>

Copies the shape of the type supplied, but marks every field optional.
https://flow.org/en/docs/types/utilities/#toc-shape

Usage:

import { $Shape } from 'utility-types';

type Props = { name: string; age: number; visible: boolean };

// Expect: Partial<Props>
type PartialProps = $Shape<Props>;

⇧ back to top

$NonMaybeType<T>

Converts a type T to a non-maybe type. In other words, the values of $NonMaybeType<T> are the values of T except for null and undefined.
https://flow.org/en/docs/types/utilities/#toc-nonmaybe

Usage:

import { $NonMaybeType } from 'utility-types';

type MaybeName = string | null;

// Expect: string
type Name = $NonMaybeType<MaybeName>;

⇧ back to top

Class<T>

Given a type T representing instances of a class C, the type Class is the type of the class C
https://flow.org/en/docs/types/utilities/#toc-class * Differs from original Flow's util - implements only constructor part and won't include any static members. Additionally classes in Typescript are not treated as nominal

Usage:

import { Class } from 'utility-types';


function makeStore(storeClass: Class<Store>): Store {
  return new storeClass();
}

⇧ back to top

mixed

An arbitrary type that could be anything (same as unknown)
https://flow.org/en/docs/types/mixed

⇧ back to top

Related Projects

  • ts-toolbelt - Higher type safety for TypeScript
  • $mol_type - Collection of TypeScript meta types for complex logic

License

MIT License

Copyright (c) 2016 Piotr Witek mailto:piotrek.witek@gmail.com (http://piotrwitek.github.io)