Utils
NonNullable
Removes `null` and `undefined` from a type.
The NonNullable<T> utility type provides a specialized implementation for removing both null and undefined from a given union type T.
It ensures that the resulting type represents a concrete value that is guaranteed to exist.
Definition
NonNullable.ts
/**
* Removes `null` and `undefined` from a type.
*/
export type NonNullable<T> = T extends null | undefined ? never : T;
Example Usage
This utility allows you to strictly enforce that a value has been initialized and is securely accessible, effectively stripping away the possibility of it being absent.
example.ts
import type { NonNullable } from '@riavzon/utils'
type MaybeString = string | null | undefined;
type MaybeUser = { id: string } | undefined;
// Evaluates to: string
type DefiniteString = NonNullable<MaybeString>;
// Evaluates to: { id: string }
type DefiniteUser = NonNullable<MaybeUser>;
function printName(name: DefiniteString) {
console.log(name.toUpperCase()); // Safe to use string methods here
}
// Allowed
printName("Sergo");
// Error: Argument of type 'null' is not assignable to parameter of type 'string'.
printName(null);
