Enums

What's enums

Enums are one of the few features TypeScript has which is not a type-level extension of JavaScript.

Enums allow a developer to define a set of named constants.

Using enums can make it easier to document intent, or create a set of distinct cases.

TypeScript provides both numeric and string-based enums.

An enum can be defined using the enum keyword.

enum Grade {
  A,
  B,
  C,
  D,
}
console.log(Grade.A, Grade.B); // 0 1

enum Direction {
  Up = 1,
  Down,
  Left,
  Right,
}
console.log(Direction.Up); // 1
console.log(Direction.Down); // 2

enum Band {
  A = 2,
  B = "string",
}

console.log(Band.A); // 2
console.log(Band.B); // string

enum Gender {
  Male = 0,
  Female = 1,
  Other = 2,
}
let person: { name: string; gender: Gender };

person = { name: "nansen", gender: Gender.Male };
// `Gender.Male` is more readable than `0`

console.log(person); // { name: 'nansen', gender: 0 }