Typescript interface allowing key of type, and string values

Question

Is there a way in Typescript to use a known type as the key of an interface, dynamically?

For example, I have this type:

type properties = 'name' | 'age' | 'height';

and I want to allow an object that uses any/all of those "properties" as the key, and a string as the value:

{name: 'abc', height: '2'} or {height: '2'} allowed

I've done this with values, but not keys, so I'd want the opposite of this:

interface person {
  [key: string]: properties
}

Something like this:

interface person {
  [key: properties]: string
}

type person = { [key in properties]?: string }

zerkms
– zerkms

2020-07-15 00:09:32 +00:00
Commented Jul 15, 2020 at 0:09 — zerkms
– zerkms, Commented Jul 15, 2020 at 0:09

Kousha · Accepted Answer · 2020-07-15 00:09:01Z

2

You can use type for that:

type Properties = 'name' | 'age' | 'height';
type Person = {
    [key in Properties]: string
}

// This is allowed
const allowed: Person = {
    name: 'the-name',
    age: '21',
    height: '180',
}

// This has error
const errored: Person = {
    name: 'the-name',
    age: '21',
    height: '180',
    anotherKey: 'foo',
}

answered Jul 15, 2020 at 0:09

Kousha

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1 Comment

d-_-b Over a year ago

thanks! i added ?: string to satisfy the optional cases.

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