Using Typescript's mapped types to apply a single value type to all values across different key types

Having two different key types, OneOf and FeildType, to distinguish between the two types, I initially tried creating the following type but it ended up combining the member types.

interface TypeMap {
    [key: number]: FeildType
    [key: string]: OneOf
}

Attempting to merge the two keys into one member like this:

interface TypeMap
    [key in (number | string)]: key extends string ? OneOf :
                                key extends number ? FeildType :
                                never
}

Unfortunately, this also resulted in the merging of the two types.

Is there a way to define this type without combining the member types, like so:

interface TypeMap {
    [key: number]: FeildType
    [key: string]: OneOf
}

Can this be achieved without merging the two member types?

typescript

Answer №1

Eureka! I've discovered that I can accomplish this using this particular type of code

type ParentType = FeildTypeMap | OneOfTypeMap

interface FeildTypeMap {
    [key: number]: FeildType
}

interface OneOfTypeMap {
    [key: string]: OneOf
}

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