How to get union types of object values inside array?

Question

For example, I have an array

const list = [{id: 'a'}, {id: 'b'}, {id: 'c'}] as const;

and I want to get union type from all values of field id, i.e. 'a'|'b'|'c'.

Nick · Accepted Answer · 2021-01-02 23:56:53Z

2

You can use typeof list[number]["id"] to get a union of all the id values.

const list = [{id: 'a'}, {id: 'b'}, {id: 'c'}] as const;
type Values = typeof list[number]["id"];

answered Jan 2, 2021 at 23:56

Nick

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4 Comments

I tried in playground, and it did not work, any specific TS settings you are using?

No, here's the playground link that's working for me: typescriptlang.org/play?#code/…

ah, I have a typo -- an extra comma in the array. so it works. thank you!

Great! No problem.