[TypeScript] "Pick" Mapped Type

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

// gives error since we didn't define 'address'
const person: Person = {
    name: "Wan",
    age: 30
}

 

We can use 'Pick' mapped type to define a subtype, we can also write on our own

type MyPcik<T, K extends keyof T> = {
    [P in K]: T[P]
}

// K extends keyof T --> 'name' | 'age'

 

Usage:

const person: MyPick<Person, 'name' | 'age'> = {
  name: 'Wan',
  age: 30    
}

 

Use built-in Pick:

const person: Pick<Person, 'name' | 'age'> = {
  name: 'Wan',
  age: 30    
}