How to add/override properties in interface in TypeScript?

Question

I have the following interface A and need to create type that extends A, but overrides definition of property type

interface A {
    type: 'user';
    name: string;
}

type B = ???

let q: B = {
    type: 'admin',
    name: 'John'
}

How to do this?

Titian Cernicova-Dragomir · Accepted Answer · 2020-05-07 12:55:14Z

1

You can use a combination of Omit in an intersection with another type that adds the property back with a different type:

type B = Omit<A, 'type'> & {
  type: "admin"
}

You can also create a more general version of this replace type:

type Replace<T, TOverride> = Omit<T, keyof TOverride> & TOverride

type B =  Replace<A,  {
  type: "admin"
}>

answered May 7, 2020 at 12:55

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Comments

Lesiak · Accepted Answer · 2020-05-07 12:55:35Z

1

type B = Omit<A, 'type'> & {type: 'admin'};

answered May 7, 2020 at 12:55

Lesiak

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