Indexed Access types provide a mechanism for retrieving part(s) of an array or object type via indices. We’ll look at how this kind of type works, and a couple of practical examples of where you might use them.
interface Car { make: string model: string year: number color: { red: string green: string blue: string } }
We can get color
type:
let carColor: Car["color"] /* let carColor: { red: string; green: string; blue: string; } */
We can get nested prop type:
let carColorRedComponent: Car["color"]["red"] // string
Index access type has safe guard:
let carColor: Car["not-something-on-car"] // ERROR: Property 'not-something-on-car' does not exist on type 'Car'.
We can get Intersection types on index access types:
let carPropertyWeInterest: Car["color" | "year", "model"] /* string | number | { red: string; green: string; blue: string; } */