Create TS Array Custom Types?

Question

Is it possible to do something like this to define a custom Companies Array type?:

export interface Company {
  name: string;
}

export interface Companies: Array<Company> {

}

it doesn't seem to like my syntax for Companies.

Or does this not make any sense to try to do at all?

is this what you mean interface Companies extends Array<Company> {}? — Pritam Kadam
– Pritam Kadam, Commented Sep 27, 2020 at 7:00
maybe, that's probably what I infer. I guess making this would allow my TS to be a little shorter than specifying Array<Company> all over the place in my code? — PositiveGuy
– PositiveGuy, Commented Sep 27, 2020 at 7:02
it sounds like both of you are showing me a way to basically kinda do the same thing right? And benefit being that it's cleaner to use in my code as well when I use that type or interface rather than specify Array<Company> all over the place right? — PositiveGuy
– PositiveGuy, Commented Sep 27, 2020 at 7:04
just in case you want to have a shorter definition, you may go with Company[] — Anton Kononenko
– Anton Kononenko, Commented Sep 27, 2020 at 8:29

cherryblossom · Accepted Answer · 2020-09-28 06:51:33Z

1

If you simply want an array of companies, you can use either one of these:

type Companies = Company[]
type Companies = Array<Company>

Alternatively, you don't even need to define a type alias and can just use Company[] or Array<Company>.

However, if you want to declare additional properties on the array, you can extend Array<Company>:

interface Companies extends Array<Company> {
  foo: string
  bar: number
}

To make such an object, you can use one of these:

declare const normalArray: Company[]

const companies1: Companies = Object.assign(normalArray, {foo: '', bar: 0})

const companies2 = normalArray as Companies
companies2.foo = ''
companies2.bar = 0

answered Sep 28, 2020 at 6:51

cherryblossom

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