A collection of essential TypeScript types. 

A collection of essential TypeScript types

sindresorhus

type-fest

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	"description": "A collection of essential TypeScript types",

		"@typescript-eslint/eslint-plugin": "^1.8.0",

		"eslint-config-xo-typescript": "^0.11.0",

A collection of essential TypeScript types

[![Build Status](https://travis-ci.com/sindresorhus/type-fest.svg?branch=master)](https://travis-ci.com/sindresorhus/type-fest)

[![](https://img.shields.io/badge/unicorn-approved-ff69b4.svg)](https://www.youtube.com/watch?v=9auOCbH5Ns4)

<!-- Commented out until they actually show anything

[![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/master/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.

type FooWithoutRainbow = Omit<Foo, 'rainbow'>;

- [`Primitive`](source/basic.d.ts) - Matches any [primitive value](https://developer.mozilla.org/en-US/docs/Glossary/Primitive).

- [`Class`](source/basic.d.ts) - Matches a [`class` constructor](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes).

- [`TypedArray`](source/basic.d.ts) - Matches any [typed array](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray), like `Uint8Array` or `Float64Array`.

- [`JsonObject`](source/basic.d.ts) - Matches a JSON object.

- [`JsonArray`](source/basic.d.ts) - Matches a JSON array.

- [`JsonValue`](source/basic.d.ts) - Matches any valid JSON value.

- [`ObservableLike`](source/basic.d.ts) - Matches a value that is like an [Observable](https://github.com/tc39/proposal-observable).

- [`Omit`](source/omit.d.ts) - Create a type from an object type without certain keys.

- [`Mutable`](source/mutable.d.ts) - Convert an object with `readonly` properties into a mutable object. Inverse of `Readonly<T>`.

- [`Merge`](source/merge.d.ts) - Merge two types into a new type. Keys of the second type overrides keys of the first type.

- [`MergeExclusive`](source/merge-exclusive.d.ts) - Create a type that has mutually exclusive properties.

- [`RequireAtLeastOne`](source/require-at-least-one.d.ts) - Create a type that requires at least one of the given properties.

- [`ReadonlyDeep`](source/readonly-deep.d.ts) - Create a deeply immutable version of a `object`/`Map`/`Set`/`Array` type.

- [`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](https://github.com/Microsoft/TypeScript/issues/29729).

- [`PackageJson`](source/package-json.d.ts) - Type for [npm's `package.json` file](https://docs.npmjs.com/creating-a-package-json-file).

*If we decline a type addition, we will make sure to document the better solution here.*

- [`Diff` and `Spread`](https://github.com/sindresorhus/type-fest/pull/7) - The PR author didn't provide any real-world use-cases and the PR went stale. If you think this type is useful, provide some real-world use-cases and we might reconsider.

There are many advanced types most users don't know about.

- [`Partial<T>`](https://github.com/Microsoft/TypeScript/blob/2961bc3fc0ea1117d4e53bc8e97fa76119bc33e3/src/lib/es5.d.ts#L1401-L1406) - Make all properties in `T` optional.

- [`Required<T>`](https://github.com/Microsoft/TypeScript/blob/2961bc3fc0ea1117d4e53bc8e97fa76119bc33e3/src/lib/es5.d.ts#L1408-L1413) - Make all properties in `T` required.

- [`Readonly<T>`](https://github.com/Microsoft/TypeScript/blob/2961bc3fc0ea1117d4e53bc8e97fa76119bc33e3/src/lib/es5.d.ts#L1415-L1420) - Make all properties in `T` readonly.

- [`Pick<T, K>`](https://github.com/Microsoft/TypeScript/blob/2961bc3fc0ea1117d4e53bc8e97fa76119bc33e3/src/lib/es5.d.ts#L1422-L1427) - From `T`, pick a set of properties whose keys are in the union `K`.

- [`Record<K, T>`](https://github.com/Microsoft/TypeScript/blob/2961bc3fc0ea1117d4e53bc8e97fa76119bc33e3/src/lib/es5.d.ts#L1429-L1434) - Construct a type with a set of properties `K` of type `T`.

- [`Exclude<T, U>`](https://github.com/Microsoft/TypeScript/blob/2961bc3fc0ea1117d4e53bc8e97fa76119bc33e3/src/lib/es5.d.ts#L1436-L1439) - Exclude from `T` those types that are assignable to `U`.

- [`Extract<T, U>`](https://github.com/Microsoft/TypeScript/blob/2961bc3fc0ea1117d4e53bc8e97fa76119bc33e3/src/lib/es5.d.ts#L1441-L1444) - Extract from `T` those types that are assignable to `U`.

- [`NonNullable<T>`](https://github.com/Microsoft/TypeScript/blob/2961bc3fc0ea1117d4e53bc8e97fa76119bc33e3/src/lib/es5.d.ts#L1446-L1449) - Exclude `null` and `undefined` from `T`.

- [`Parameters<T>`](https://github.com/Microsoft/TypeScript/blob/2961bc3fc0ea1117d4e53bc8e97fa76119bc33e3/src/lib/es5.d.ts#L1451-L1454) - Obtain the parameters of a function type in a tuple.

- [`ConstructorParameters<T>`](https://github.com/Microsoft/TypeScript/blob/2961bc3fc0ea1117d4e53bc8e97fa76119bc33e3/src/lib/es5.d.ts#L1456-L1459) - Obtain the parameters of a constructor function type in a tuple.

- [`ReturnType<T>`](https://github.com/Microsoft/TypeScript/blob/2961bc3fc0ea1117d4e53bc8e97fa76119bc33e3/src/lib/es5.d.ts#L1461-L1464) – Obtain the return type of a function type.

- [`InstanceType<T>`](https://github.com/Microsoft/TypeScript/blob/2961bc3fc0ea1117d4e53bc8e97fa76119bc33e3/src/lib/es5.d.ts#L1466-L1469) – Obtain the instance type of a constructor function type.

You can find some examples in the [TypeScript docs](https://www.typescriptlang.org/docs/handbook/advanced-types.html#predefined-conditional-types).

- [Sindre Sorhus](https://github.com/sindresorhus)

- [Dimitri Benin](https://github.com/BendingBender)

		{
		"name": "type-fest",
		"version": "0.5.1",
		"version": "0.5.2",
		"description": "A collection of essential TypeScript types",
		@@ -40,5 +40,2 @@ "license": "(MIT OR CC0-1.0)",
		},
		"peerDependencies": {
		"typescript": ">=3.2"
		},
		"xo": {
		@@ -45,0 +42,0 @@ "extends": "xo-typescript",

		@@ -33,3 +33,5 @@ <div align="center">

		Requires TypeScript >=3.2


		## Usage
		@@ -36,0 +38,0 @@

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