Remove nullable property from a custom object type

Question

I'm trying to create a type that has null void and undefined removed.

type TEST = {
  propOne:string
  propTwo: number
  propThree:null  // completely remove this property
}

type CLEAN<T> = { [P in keyof T]: NonNullable<T[P]> };

type FIXED = CLEAN<TEST>

const fixed:FIXED={ // error - it wants propThree property
    propOne:'',
    propTwo:1,
}

TS Playground

I cant give you a complete solution, but seems its achieveable with pick - ideasintosoftware.com/typescript-advanced-tricks — lucifer63
– lucifer63, Commented Sep 25, 2021 at 23:04

akuiper · Accepted Answer · 2021-09-26 00:34:22Z

1

You can use key remapping with conditional types to map nullable keys to never which will remove the property from the result type:

type CLEAN<T> = { [P in keyof T as null extends T[P] ? never : P]: T[P] };

Playground

answered Sep 26, 2021 at 0:34

akuiper

216k33 gold badges363 silver badges380 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Ivan V. · Accepted Answer · 2021-09-26 20:28:01Z

1

@Psidom Thank you, your answer got me on the right path. However, I've said a need null void and undefined removed. So following the documentation link about key remapping that you posted I've come up with this solution.

type TEST = {
  propOne:string
  propTwo: number
  propThree:void  // completely remove this property
}

type CLEAN<T,K> = { [P in keyof T as T[P] extends K ? never : P]: T[P] };

const fixed:CLEAN<TEST,void | null | undefined>={
    propOne:'',
    propTwo:1,
}

This way I can omit any number of types.

Playground

edited Sep 26, 2021 at 20:28

answered Sep 26, 2021 at 20:18

Ivan V.

8,1692 gold badges39 silver badges56 bronze badges

Collectives™ on Stack Overflow

Remove nullable property from a custom object type

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related