typescript pick type code example

Example 1: typescript keyof

interface Person {
  name: string;
  age: number;
  location: string;
}

type K1 = keyof Person; // "name" | "age" | "location"
type K2 = keyof Person[]; // "length" | "push" | "pop" | "concat" | ...
type K3 = keyof { [x: string]: Person }; // string

Example 2: typescript pick

type TodoPreview = Pick<Todo, "title" | "completed">;

Example 3: typescript utility types merge interfaces

interface A {
    x: string
}

interface B extends Omit<A, 'x'> {
  x: number
}