Q23: How do Indexed Access Types (`T[K]`) work?
An Indexed Access Type looks up specific sub-properties on another type using bracket notation syntax (Type[Key]).
Property Type Lookup
interface Order {
id: string;
customer: {
name: string;
address: { city: string };
};
}
type CustomerType = Order["customer"]; // Type: { name: string; address: { city: string } }
type CityType = Order["customer"]["address"]["city"]; // Type: string💡 Bracket notation pulls property types from complex nested object structures.
Key Takeaways
- Look up property types dynamically from existing structural contracts.