typescript generic array doesn't work typescript 3.9.7

Question

This works in typescript v4.1.3(playground) but doesn't work in v3.9.7(playground)

const uniqueMap = <K, V>(items: [key: K, val: V][]) =>
    new Map(items).values()

How to make this work. I am trying to make it generic so that I can use it for any kind of data.

My current work around

const uniqueMap = (items: any[]) => new Map(items).values()

You are using new feature from ts 4, that is why it is not working in ts 3.9. Have a look: typescriptlang.org/docs/handbook/release-notes/…. I would suggest not to use labels as your ts compiler doesn't support it — mashi
– mashi, Commented Feb 4, 2021 at 9:17

Brian Burton · Accepted Answer · 2021-02-04 09:07:13Z

1

Tuple labels are a TS 4.0 feature and not really all that useful, imo. Simplifying your code like this makes it compatible in all modern versions of TS:

const uniqueMap = <K, V>(items: [K, V][]) =>
    new Map(items).values()

Playground

answered Feb 4, 2021 at 9:07

Brian Burton

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