枚举

枚举与数字兼容，数字与枚举兼容。来自不同枚举类型的枚举值被认为是不兼容的。例如，

Enums are compatible with numbers, and numbers are compatible with enums. Enum values from different enum types are considered incompatible. For example,

enum Status {
  Ready,
  Waiting,
}
enum Color {
  Red,
  Blue,
  Green,
}

let status = Status.Ready;
status = Color.Green; // Error