Allow any subset of specified array in Typescript

Question

Can I specify an array as a type in Typescript and then any subset of this array is allowed to be passed?

E.g.

type Actions = ['view', 'share', 'delete']

const concatActions = (actions: Actions) => actions.join();

concatActions(['view', 'delete']) // Works
concatActions(['share']) // Works
concatActions(['view', 'some_other_action']) // Throws type error

jasper · Accepted Answer · 2019-11-20 11:45:16Z

2

This should work

type Action = 'view' | 'share' | 'delete'
type Actions = Action[]

answered Nov 20, 2019 at 11:45

jasper

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2 Comments

dorondo Over a year ago

Is there a way also to disallow duplicates? so that ['share', 'view', 'share'] is not allowed.

jasper Over a year ago

I don't think so, not TypeScript natively at least. The solution would be to prevent dupes in concatActions. You can create a new SO question and send it to me if you wonder how to do that. Let's stay on topic :)

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