sindresorhus / type-fest

A collection of essential TypeScript types Sindre Sorhus' open source work is supported by the community Special thanks to: Effortless backends with infrastructure from code An open-source framework that supports any programming language, cloud provider, or deployment automation tool. Many of the types here should have been built-in. You can help by suggesting some of them to the TypeScript project. 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 first. **Help wanted with reviewing proposals and pull requests.** Install *Requires TypeScript >=5.9, ESM, and in your tsconfig.* > [!NOTE] > This readme shows the current development version. For docs about the latest version, see the npm page. *You may also like my package which provides runtime functions for some of these types.* Usage API Click the type names for complete docs. Basic • - Matches any primitive value. • - Matches a . • - Matches a constructor. • - Matches an . • - Matches an constructor. • - Matches any typed array, like or . • - Matches a value that is like an Observable. • - Matches any lowercase letter in the basic Latin alphabet (a-z). • - Matches any uppercase letter in the basic Latin alphabet (A-Z). • - Matches any digit as a string ('0'-'9'). • - Matches any lowercase letter (a-z), uppercase letter (A-Z), or digit ('0'-'9') in the basic Latin alphabet. Utilities • - Represents a strictly empty plain object, the value. • - Represents an object with at least 1 non-optional key. • - Represents an object with value. You probably want this instead of . • - Represents an array with value. • - Represents a map with key and value. • - Represents a set with value. • - Create a type from an object type without certain keys. This is a stricter version of . • - Create a type that strips from the given type. Inverse of . • - Create a deeply mutable version of an / / / type. The inverse of . Use if you only need one level deep. • - Merge two types into a new type. Keys of the second type overrides keys of the first type. • - Merge two object types into a new object type, where keys from the second override keys from the first. • - Merge two objects or two arrays/tuples recursively into a new type. • - Create a type that has mutually exclusive keys. • - Override only existing properties of the given type. Similar to , but enforces that the original type has the properties you want to override. • - Create a type that requires at least one of the given keys. • - Create a type that requires exactly a single key of the given keys and disallows more. • - Create a type that requires all of the given keys or none of the given keys. • - Create a type that requires exactly a single key of the given keys and disallows more, or none of the given keys. • - Create a type that only accepts an object with a single key. • - Create a deeply required version of another type. Use if you only need one level deep. • - Pick properties from a deeply-nested object. Use if you only need one level deep. • - Omit properties from a deeply-nested object. Use if you only need one level deep. • - Omit any index signatures from the given object type, leaving only explicitly defined properties. • - Pick only index signatures from the given object type, leaving out all explicitly defined properties. • - Create a deeply optional version of another type. Use if you only need one level deep. • - Create a deep version of another type where all keys accepting type are set to optional. • - Create a deep version of another type where all optional keys are set to also accept . • - Revert the modifier on an object type. • - Create a deeply immutable version of an / / / type. Use if you only need one level deep. • - 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. • - Create a tagged type that can support multiple tags and per-tag metadata. (This replaces the previous type, which is now deprecated.) • - Get the untagged portion of a tagged type created with . (This replaces the previous type, which is now deprecated.) • - Create an invariant type, which is a type that does not accept supertypes and subtypes. • - Create a type that makes the given keys optional. • - Create a type that makes the given keys readonly. • - Create a type that makes the given keys required. • - Like except it selects the keys deeply. • - Create a type that makes the given keys non-nullable. • - Create a type that makes the specified keys non-nullable (removes and ), supports deeply nested key paths, and leaves all other keys unchanged. • - Create a union of the given object's values, and optionally specify which keys to get the values from. • - Extract keys from a shape where values extend the given type. • - Like except it selects properties from a shape where the values extend the given type. • - Like except that it selects the properties deeply. • - Like except it removes properties from a shape where the values extend the given type. • - Convert a union type to an intersection type. • - Convert a literal type to the primitive type it belongs to. • - Like except it converts literal types inside an object or array deeply. • - Create a type with the keys of the given type changed to type. • - Get the element type of an / . For example, , , , generator, stream, etc. • - Create a type that represents the type of an entry of a collection. • - Create a type that represents the type of the entries of a collection. • - Create a function type with a return type of your choice and the same parameters as the given function type. • - Create a function that replaces some parameters with the given parameters. • - Useful to flatten the type output to improve type hints shown in editors. And also to t…