value union type

객체의 필드의 values 값들을 유니언타입으로 설정하고 싶을 경우

export const events = {
  GET_EXTENSION_ID: "HORSY_GET_EXTENSION_ID",
  SAVE_SETTING: "HORSY_SAVE_SETTING",
  UPDATE_SETTING: "HORSY_UPDATE_SETTING",
  GET_SETTING: "HORSY_GET_SETTING",
  GET_USER: "HORSY_GET_USER",
  OPEN_SETTING_PAGE: "HORSY_OPEN_SETTING_PAGE",
} as const;

export type EventType = (typeof events)[keyof typeof events];
/* "HORSY_GET_EXTENSION_ID" | "HORSY_SAVE_SETTING" | "HORSY_UPDATE_SETTING" | "HORSY_GET_SETTING" | "HORSY_GET_USER" | "HORSY_OPEN_SETTING_PAGE"
*/

as const 를 제외하면 단순 string으로 추론된다.