Typescript use optional generic

Question

I have the following function:

function prop<T extends Record<any, any>, K extends keyof T>(key: K): T[K] {
   
}

const v = prop<{ test: string }>('test')

The issue is that I must pass a second generic to correctly infer the key. Is there any way to skip the second generic and still infer the key as keyof T?

I don't want to do the following:

prop<{ test: string }, 'test'>('test')

zixiCat · Accepted Answer · 2021-04-29 09:11:26Z

1

You could try to use default generic like this one:

function prop<T extends Record<any, any>, K = keyof T>(key: K): T[K] {
   
}

const v1 = prop<{ test: string }>('test') // OK
const v2 = prop<{ test: string }>('test12') // ERROR

answered Apr 29, 2021 at 9:11

zixiCat

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