索引访问类型(Indexed Access Types)

type Person = { age: number; name: string; alive: boolean };
type Age = Person["age"];



type I1 = Person["age" | "name"];
type I2 = Person[keyof Person];
type AliveOrName = "alive" | "name";
type I3 = Person[AliveOrName];




const MyArray = [
  { name: "Alice", age: 15 },
  { name: "Bob", age: 23 },
  { name: "Eve", age: 38 },
];
type Person = typeof MyArray[number];
type Age = typeof MyArray[number]["age"];
type Age2 = Person["age"];





type key = "age";
type Age = Person[key];