typescript - remove null or undefined from properties of a type

Question

I need to declare a type such that removes the undefined from its property types.

Suppose we have:

type Type1{
  prop?: number;
}

type Type2{
  prop: number | undefined;
}

type Type3{
  prop: number;
}

I need to define a generic type called NoUndefinedField<T> such that NoUndefinedField<Type1> gives the same type as Type3 and the same type as NoUndefinedField<Type2>.

I tried this

type NoUndefinedField<T> = { [P in keyof T]: Exclude<T[P], null | undefined> };

But it only works for Type2.

question from:https://stackoverflow.com/questions/53050011/remove-null-or-undefined-from-properties-of-a-type

Answer 1

There is also now the NonNullable type built in:

type NonNullable<T> = Exclude<T, null | undefined>;  // Remove null and undefined from T

https://www.typescriptlang.org/docs/handbook/utility-types.html#nonnullablet