❌

interface User {
  name: string;
  age: number;
}

let user2:User = {
  name: 'aaa',
  age: 30,
}

console.log(user2.name)
console.log(user2.age)
console.log(user2.gender)

❌

interface User {
  name: string;
  age: number;
}

let user2:User = {
  name: 'aaa',
  age: 30,
  gender: "male"
}

console.log(user2.name)
console.log(user2.age)
console.log(user2.gender)

⭕️ 1-1.

interface User {
  name: string;
  age: number;
  gender?: string;
}

let user2:User = {
  name: 'aaa',
  age: 30,
}

console.log(user2.name)
console.log(user2.age)
console.log(user2.gender)

물음표가 붙은 interface의 key값은 있어도 되고, 없어도 되는 옵셔널한 값이다.

⭕️1-2.

interface User {
  name: string;
  age: number;
  gender?: string;
}

let user2:User = {
  name: 'aaa',
  age: 30,
  gender: "male"
}

console.log(user2.name)
console.log(user2.age)
console.log(user2.gender)