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<b>A collection of essential TypeScript types</b>
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[![](https://img.shields.io/badge/unicorn-approved-ff69b4.svg)](https://giphy.com/gifs/illustration-rainbow-unicorn-26AHG5KGFxSkUWw1i)
[![npm dependents](https://badgen.net/npm/dependents/type-fest)](https://www.npmjs.com/package/type-fest?activeTab=dependents)
[![npm downloads](https://badgen.net/npm/dt/type-fest)](https://www.npmjs.com/package/type-fest)
Many of the types here should have been built-in. You can help by suggesting some of them to the [TypeScript project](https://github.com/Microsoft/TypeScript/blob/main/CONTRIBUTING.md).
Either add this package as a dependency or copy-paste the needed types. No credit required. ����
PR welcome for additional commonly needed types and docs improvements. Read the [contributing guidelines](.github/contributing.md) first.
**Help wanted with reviewing [proposals](https://github.com/sindresorhus/type-fest/issues) and [pull requests](https://github.com/sindresorhus/type-fest/pulls).**
## Install
```sh
npm install type-fest
```
*Requires TypeScript >=5.1*
*Works best with [`{strict: true}`](https://www.typescriptlang.org/tsconfig#strict) in your tsconfig.*
## Usage
```ts
import type {Except} from 'type-fest';
type Foo = {
unicorn: string;
rainbow: boolean;
};
type FooWithoutRainbow = Except<Foo, 'rainbow'>;
//=> {unicorn: string}
```
## API
Click the type names for complete docs.
### Basic
- [`Primitive`](source/primitive.d.ts) - Matches any [primitive value](https://developer.mozilla.org/en-US/docs/Glossary/Primitive).
- [`Class`](source/basic.d.ts) - Matches a [`class`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes).
- [`Constructor`](source/basic.d.ts) - Matches a [`class` constructor](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes).
- [`AbstractClass`](source/basic.d.ts) - Matches an [`abstract class`](https://www.typescriptlang.org/docs/handbook/classes.html#abstract-classes).
- [`AbstractConstructor`](source/basic.d.ts) - Matches an [`abstract class`](https://www.typescriptlang.org/docs/handbook/release-notes/typescript-4-2.html#abstract-construct-signatures) constructor.
- [`TypedArray`](source/typed-array.d.ts) - Matches any [typed array](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray), like `Uint8Array` or `Float64Array`.
- [`ObservableLike`](source/observable-like.d.ts) - Matches a value that is like an [Observable](https://github.com/tc39/proposal-observable).
### Utilities
- [`EmptyObject`](source/empty-object.d.ts) - Represents a strictly empty plain object, the `{}` value.
- [`IsEmptyObject`](source/empty-object.d.ts) - Returns a `boolean` for whether the type is strictly equal to an empty plain object, the `{}` value.
- [`NonEmptyObject`](source/non-empty-object.d.ts) - Represents an object with at least 1 non-optional key.
- [`UnknownRecord`](source/unknown-record.d.ts) - Represents an object with `unknown` value. You probably want this instead of `{}`.
- [`Except`](source/except.d.ts) - Create a type from an object type without certain keys. This is a stricter version of [`Omit`](https://www.typescriptlang.org/docs/handbook/utility-types.html#omittype-keys).
- [`Writable`](source/writable.d.ts) - Create a type that strips `readonly` from all or some of an object's keys. The inverse of `Readonly<T>`.
- [`WritableDeep`](source/writable-deep.d.ts) - Create a deeply mutable version of an `object`/`ReadonlyMap`/`ReadonlySet`/`ReadonlyArray` type. The inverse of `ReadonlyDeep<T>`. Use `Writable<T>` if you only need one level deep.
- [`Merge`](source/merge.d.ts) - Merge two types into a new type. Keys of the second type overrides keys of the first type.
- [`MergeDeep`](source/merge-deep.d.ts) - Merge two objects or two arrays/tuples recursively into a new type.
- [`MergeExclusive`](source/merge-exclusive.d.ts) - Create a type that has mutually exclusive keys.
- [`OverrideProperties`](source/override-properties.d.ts) - Override only existing properties of the given type. Similar to `Merge`, but enforces that the original type has the properties you want to override.
- [`RequireAtLeastOne`](source/require-at-least-one.d.ts) - Create a type that requires at least one of the given keys.
- [`RequireExactlyOne`](source/require-exactly-one.d.ts) - Create a type that requires exactly a single key of the given keys and disallows more.
- [`RequireAllOrNone`](source/require-all-or-none.d.ts) - Create a type that requires all of the given keys or none of the given keys.
- [`RequireOneOrNone`](source/require-one-or-none.d.ts) - Create a type that requires exactly a single key of the given keys and disallows more, or none of the given keys.
- [`RequiredDeep`](source/required-deep.d.ts) - Create a deeply required version of another type. Use [`Required<T>`](https://www.typescriptlang.org/docs/handbook/utility-types.html#requiredtype) if you only need one level deep.
- [`OmitIndexSignature`](source/omit-index-signature.d.ts) - Omit any index signatures from the given object type, leaving only explicitly defined properties.
- [`PickIndexSignature`](source/pick-index-signature.d.ts) - Pick only index signatures from the given object type, leaving out all explicitly defined properties.
- [`PartialDeep`](source/partial-deep.d.ts) - Create a deeply optional version of another type. Use [`Partial<T>`](https://www.typescriptlang.org/docs/handbook/utility-types.html#partialtype) if you only need one level deep.
- [`PartialOnUndefinedDeep`](source/partial-on-undefined-deep.d.ts) - Create a deep version of another type where all keys accepting `undefined` type are set to optional.
- [`UndefinedOnPartialDeep`](source/undefined-on-partial-deep.d.ts) - Create a deep version of another type where all optional keys are set to also accept `undefined`.
- [`ReadonlyDeep`](source/readonly-deep.d.ts) - Create a deeply immutable version of an `object`/`Map`/`Set`/`Array` type. Use [`Readonly<T>`](https://www.typescriptlang.org/docs/handbook/utility-types.html#readonlytype) if you only need one level deep.
- [`LiteralUnion`](source/literal-union.d.ts) - Create a union type by combining primitive types and literal types without sacrificing auto-completion in IDEs for the literal type part of the union. Workaround for [Microsoft/TypeScript#29729