Is there some way to extract property values from array?
const d = [{id: 'Cat'}, {id: 'Dog'}]
type ids = ??? //insert code here, type should be 'Cat' | 'Dog'
(It would also work if it generates a const enum)
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1 Answer
When you declare d with as const, you can extract the information like this:
const d = [{id: 'Cat'}, {id: 'Dog'}] as const
type IDs = typeof d[number]["id"]
4 Comments
JoannaFalkowska
To add an explanation why
as const is needed: literal types won't work otherwise, so you'd only be able to get the less strict string. typescriptlang.org/docs/handbook/2/…
Peter
is it possible to do
as const when importing a json file?
Tobias S.
I would say no. It would not work with an imported json file. This only works with object literals in your typescript code.
Tobias S.
Here is an open issue github.com/microsoft/TypeScript/issues/32063 for allowing to import json with
as const. So this may be possible in the future.