utility-types
Advanced tools
The utility-types package provides a collection of utility types for TypeScript, which can be used to manipulate and transform type definitions in a type-safe manner. It includes types for common operations like picking, omitting, and mapping properties of other types, as well as more advanced utility types for conditional types, type inference, and more.
Transformation Types
Transformation types allow you to create new types based on existing ones by picking, omitting, or modifying their properties. For example, $Keys<T> extracts the keys of an object type T.
{"$Keys<T>": "Extracts the keys of an object type T as a union of literal types."}Conditional Types
Conditional types enable you to create types that depend on a condition. For instance, $Diff<T, U> creates a type by removing properties from T that are also in U.
{"$Diff<T, U>": "Computes the set difference of types T and U, essentially removing properties from T that are in U."}Mapped Types
Mapped types allow you to create new types by transforming properties of an existing type. $Call<F, T> is used to infer the return type of a function type F.
{"$Call<F, T>": "Infers the return type of a function type F when called with arguments of type T."}Type Inference Helpers
Type inference helpers assist in inferring types within other types. $ElementType<T, K> extracts the type of property K from type T.
{"$ElementType<T, K>": "Extracts the type of a property K from type T."}ts-essentials offers a wide range of utility types for TypeScript, similar to utility-types. It includes deep read-only types, writable types, and many more. It is comparable to utility-types but may have a different set of utilities or slightly different implementations.
type-fest is a collection of essential TypeScript types, with a focus on providing a rich set of utility types. It has a broad range of types, some of which overlap with utility-types, but it also includes unique types that cater to different use cases.
type-zoo contains a zoo of utility types for TypeScript. It is similar to utility-types in that it provides a variety of helper types to manipulate and compose TypeScript types. The specific types offered and their API might differ from utility-types.
Collection of utility types, complementing TypeScript built-in mapped types and aliases (think "lodash" for static types).
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The primary goal of this library is to provide a set of proven Utility Types that should complement existing TypeScript Mapped Types.
The secondary goal is to provide a few additional utility types compatible with Flow's Utility Types helping with gradual migration between "Flow" and "TypeScript" projects.
dts-jestnpm install --save utility-types
We are open for contributions. If you're planning to contribute please make sure to read the contributing guide: CONTRIBUTING.md
Utility-Types is an independent open-source project created by people investing their free time for the benefit of our community.
If you are using Utility-Types please consider donating as this will guarantee the project will be updated and maintained in the long run.
Issues can be funded by anyone and the money will be transparently distributed to the contributors handling a particular issue.
SetIntersection<A, B>SetDifference<A, B>SetComplement<A, A1>SymmetricDifference<A, B>Exclude<A, B> (built-in)Extract<A, B> (built-in)NonNullable<T> (built-in)NonUndefined<T>FunctionKeys<T>NonFunctionKeys<T>ReadonlyKeys<T>WritableKeys<T>RequiredKeys<T>Optional<T>OptionalKeys<T>Partial<T> (built-in)DeepPartial<T>Required<T> (built-in)DeepRequired<T>Readonly<T> (built-in)DeepReadonly<T>Pick<T, K> (built-in)Omit<T, K>PickByValue<T, ValueType>OmitByValue<T, ValueType>Intersection<T, U>Diff<T, U>Subtract<T, T1>Overwrite<T, U>Assign<T, U>ReturnType<T> (built-in)InstanceType<T> (built-in)PromiseType<T>Unionize<T>Brand<T, U>$Keys<T>$Values<T>$ReadOnly<T>$Diff<T, U>$PropertyType<T, K>$ElementType<T, K>$Call<T>$Shape<T>$NonMaybeType<T>Class<T>mixedgetReturnOfExpression() - from TS v2.0 it's better to use type-level ReturnType insteadPrimitiveType representing primitive types in TypeScript: number | boolean | string | symbol
FalseyType representing falsey values in TypeScript: null | undefined | false | 0 | ''
Except
NaNwhich cannot be represented as a type literal
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>;
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>;
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'>;
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'>;
NonNullable<A>Exclude null and undefined from set A
NonUndefined<A>Exclude undefined from set A
Exclude<A, B>Exclude subset B from set A
Extract<A, B>Extract subset B from set A
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 FunctionKeysProps = FunctionKeys<MixedProps>;
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 NonFunctionKeysProps = NonFunctionKeys<MixedProps>;
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 ReadonlyProps = ReadonlyKeys<Props>;
WritableKeys<T>Get union type of keys that are writable (not readonly) in object type T
Usage:
import { WritableKeys } from 'utility-types';
type Props = { readonly foo: string; bar: number };
// Expect: "bar"
type WritableProps = WritableKeys<Props>;
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 RequiredProps = ReadonlyKeys<Props>;
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; visilbe: boolean; };
// Expect: { name?: string; age?: number; visilbe?: boolean; }
type Props = Optional<Props>
// Expect: { name: string; age?: number; visilbe?: boolean; }
type Props = Optional<Props, 'age' | 'visilbe'>;
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 OptionalProps = OptionalKeys<Props>;
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'>;
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>;
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>;
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'>;
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>;
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>;
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>;
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>;
Subtract<T, T1>From T remove properties that exist in T1 (T1 is a subtype 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>;
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>;
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: number; visible: boolean; other: string; }
type ExtendedProps = Assign<Props, NewProps>;
Partial<T>Make all properties of object type optional
Required<T>Make all properties of object type non-optional
Readonly<T>Make all properties of object type readonly
ReturnType<T>Obtain the return type of a function
InstanceType<T>Obtain the instance type of a class
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>;
PromiseType<T>Obtain Promise resolve type
Usage:
import { PromiseType } from 'utility-types';
// Expect: string
type Response = PromiseType<Promise<string>>;
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>;
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>;
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>;
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>;
Brand<T, U>Define nominal type of U based on type of T.
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"'.
$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>;
$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>;
$ReadOnly<T>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 | undefined; visible: boolean; }>
type ReadOnlyProps = $ReadOnly<Props>;
$Diff<T, U>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>;
$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'>;
$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>;
$Call<T>get the return type of a given expression type https://flow.org/en/docs/types/utilities/#toc-call
Usage:
import { $Call } from 'utility-types';
// Common use-case
const add = (amount: number) => ({ type: 'ADD' as 'ADD', payload: amount });
type AddAction = $Call<typeof returnOfIncrement>; // { 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
$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>;
$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>;
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();
}
An arbitrary type that could be anything (same as unknown)
https://flow.org/en/docs/types/mixed
MIT License
Copyright (c) 2016 Piotr Witek mailto:piotrek.witek@gmail.com (http://piotrwitek.github.io)
FAQs
Utility Types Collection for TypeScript
The npm package utility-types receives a total of 1,928,870 weekly downloads. As such, utility-types popularity was classified as popular.
We found that utility-types demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 1 open source maintainer collaborating on the project.
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