How to use `enum` values as strictly typed object keys in TypeScript.

enum-keys.ts

enum DialogButton {
  YES = "yes",
  NO = "no",
  CANCEL = "cancel"
}

interface IDialog {
  buttons: { [B in DialogButton]?: boolean },
  callback: (button: DialogButton) => void
}

const dialog: IDialog = {
  buttons: {
    [DialogButton.YES]: true,
    [DialogButton.NO]: false
  },
  callback(button) {
    console.log(button)
  }
}

console.log(DialogButton.YES in dialog.buttons) // true
console.log(DialogButton.NO in dialog.buttons) // true
console.log(DialogButton.CANCEL in dialog.buttons) // false

console.log(dialog.buttons[DialogButton.YES]) // true
console.log(dialog.buttons[DialogButton.NO]) // false
console.log(dialog.buttons[DialogButton.CANCEL]) // undefined

dialog.callback(DialogButton.YES) // yes
dialog.callback(DialogButton.NO) // no
dialog.callback(DialogButton.CANCEL) // cancel