keyof typeof typesomething

이런게 되는구나 싶네요.

type CalculatorProps = {
  left: number
  operator: keyof typeof operations
  right: number
}

type operations = {
  '+': (left: number, right: number) => number
  '-': (left: number, right: number) => number
  '*': (left: number, right: number) => number
  '/': (left: number, right: number) => number
}

 

operations 타입의 모든 key를 뽑아 CalculatorProps.operator의 유니온 타입으로 적용합니다.