Undefinable

Provide one type to the Undefinable function and it will return a type guard that will check if the value conforms to the specified type, or undefined.

Note, this type is just a Union of the specified type and Undefined.

Usage

import { T } from "type-guarder";
 
T.Undefinable(T.Number()).conforms(undefined); // true
T.Undefinable(T.Number()).conforms(3); // true
T.Undefinable(T.Number()).conforms("Hello, world"); // false
T.Undefinable(T.Number()).conforms(null); // false
T.Undefinable(T.Number()).conforms(true); // false

Nullable Optional