What does this symbol represent in the mobx documentation? an array as another array exported type

Question

In this link: https://mobx-react.js.org/recipes-context line 10 of the create store there is:

 friends: [] as TFriend[],

What does this mean? Is this Javascript or is this specifically for MobX?

In the beginning theres:

export type TFriend = {
  name: string
  isFavorite: boolean
  isSingle: boolean
}

Why is there a need to call friends an array as the export type?

Answer 1

this line is a typescript line => docs

'as' is the recommended syntax for casting in typescript. so the line of code is equivalent to:

friends: <TFriend[]> []