Interface vs Types

[yukinoda]

This is the conclusion we had in the admin panel template discussion
ml-opensource/admin-panel-template-reactjs#88 (comment)

[jinmayamashita]

my opinion is Props:

Reason, discriminated union cannot be expressed using an interface.
so as an example:

// Props is a discriminated union of 2 object type
type Props = {
    isAdmin?: false, adminData?: never
} | {
    isAdmin: true, adminData: {
        foo: string,
        bar: number
    }
}

//  TYPE ERROR: because when isAdmin is false, it does not have adminData attribute.
const props: Props  = {
    isAdmin: false,
    adminData: {
        foo: 'foo',
        bar: 123
    }
}

TypeScript Playground

// interface may also be possible with the following writing style? ... 🤔 
interface IPropsIsAdminTrue {
    isAdmin?: false, adminData?: never
}
interface IPropsIsAdminFalse {
    isAdmin: true, adminData: {
        foo: string,
        bar: number
    }
}
const props: IPropsIsAdminTrue | IPropsIsAdminFalse