If now I have an array keys:
const keys = ['firstname', 'lastname']
Can I map all the items as the key of NewType like this below?
type NewType = {
firstname: any
lastname: any
}
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1 Answer
First you need to use as const syntax to tell TS your array values won't change:
const keys = ['firstname', 'lastname'] as const;
Then you can create a union type from the array values:
type Union = typeof keys[number]; // type Union = "firstname" | "lastname"
And then use mapped types to create the NewType like so:
type Obj = {
[k in Union]: any;
}
// type Obj = {
// firstname: any;
// lastname: any;
// }
const obj: Obj = {
firstname: '',
lastname: ''
}
answered Oct 18, 2021 at 10:02
Roberto Zvjerković
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4 Comments
Keith
A little shorthand you could use ->
type Obj = Record<typeof keys[number], any>;
Roberto Zvjerković
@Keith I know, I just wanted to explain it step by step so it's easier to understand to the person that has asked the question. Thanks!
Keith
Yes, that's fine. But for anybody coming across this post, it might help to also show the Record type, as it's a tad easier to reason with. Showing how to do it manually is certainly not a bad thing to show too :)
Chosan
the
as const syntax is really helpful, thanks, nice guys!