Types

Types: TypeScript utility types.

Export	What it does
AnyFunction	A type for any function, for generic constraints such as F extends AnyFunction (safer than Function, which also accepts classes and has an untyped call).
Awaitable	A value that is returned directly or through a promise: the result of a callback that may be sync or async.
Brand	A nominal type: a T that cannot be mixed up with another T of a different brand.
Constructor	A type for any class producing a T: mixins, dependency injection tokens, instanceof helpers.
DeepPartial	Makes every property optional, at every depth: a patch of a nested settings object, read-only since a patch is only read.
DeepReadonly	Makes every property and array read-only, at every depth: a frozen configuration, a state snapshot that must not be changed in place.
ElementOf	Reads the item type of an array or tuple, such as the type of a const list of options.
Entries	The [key, value] pairs of an object type, each key with its own value type: the precise type of Object.entries, which widens keys to string.
FirstParameter	Reads the type of the first parameter of a function, such as the event of a handler.
KeysOfType	Lists the keys of the properties whose type matches: the numeric fields of a record to chart, the boolean flags of a settings object.
LiteralUnion	A union of known literals that still accepts any value of the base type, without losing autocompletion of the literals (a plain 'a' | 'b' | string collapses to string).
Merge	Combines two object types, the properties of the second replacing those of the first (like an object spread { ...a, ...b }), where an intersection would give never for conflicting properties.
Mutable	Removes readonly from the properties of a type, one level deep: a builder filling an object before handing it out as read-only.
NonEmptyArray	An array with at least one item, so that its first item is never undefined.
Nullable	A T that may be null.
Nullish	A T that may be null or undefined.
Optional	A T that may be undefined.
PartialKeys	Makes some properties optional: the input of a factory that fills them with defaults.
PickByType	Keeps the properties whose type matches.
RequireKeys	Makes some optional properties required: the result of filling in defaults.
Simplify	Flattens intersections and mapped types into a plain object type, so that editor tooltips show the properties instead of A & Omit<B, 'c'>.
UnionToIntersection	Turns a union into the intersection of its members: A | B gives A & B, to merge the types of a list of mixins or handlers.
ValueOf	The union of the value types of an object type, such as a const object used as an enum.