How to extract a new type alias from an object's value

Question

How to extract a new type alias from an object's value

const test = {
'a': ['music','bbq','shopping'],
'b': ['move','work']
};

How to get it from a test object

type Types = 'music' | 'bbq' | 'shopping' | 'move' | 'work'

Answer 1

You can do this quite easily using as const:

const test = {
'a': ['music','bbq','shopping'],
'b': ['move','work']
} as const;

type Elements = typeof test[keyof typeof test][number];

The only solution I can think of that is not using as const is defining an interface with the exact elements of the arrays:

interface Foo {
    a: ['music', 'bbq', 'shopping'],
    b: ['move', 'work']
};

type Elements2 = Foo[keyof Foo][number];