TypeScript: remap union type with values from object type

Question

Is it possible to remap typescript union type with values form object type?

e.g. what I have in mid:

type Union = 'item-type' | 'category';
type Special = {
    'item-type': 'itemType';
};

type RemapedValue = [... some realy awesome typescript ...] // => 'itemType' | 'category'

Aleksandre Javakhishvili · Accepted Answer · 2020-03-18 22:00:01Z

3

I have tried to write as clear as possible. It is like a hack, but does the job I think.

type Union = 'item-type' | 'category' | "test2" | "test-3";
type Special = {
    'item-type': 'itemType';
    'test-3': "test";
};

type UnionExtra = Special & {
    [P in Union]: P
};

type Outersect = {
    [P in keyof UnionExtra]: UnionExtra[P]
}[Union]

type Innersect = {
    [P in (Union & keyof Special)]: Special[P]
}[keyof Special]

type Result = Outersect | Innersect;

answered Mar 18, 2020 at 22:00

Aleksandre Javakhishvili

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2 Comments

zimex Over a year ago

Is it possible to make that object key value from type Special would not be mandatory in type Union? e.g. Playground Link

Aleksandre Javakhishvili Over a year ago

Try this Playground link

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