Enums

An enum defines a fixed set of named values — useful whenever a variable should only ever be one of a small, known set of options, like a status or a direction.

enum Status {
  Pending,
  Active,
  Completed,
}

let current: Status = Status.Active;
console.log(current);
console.log(Status[current]);

1
Active

By default, enum members are numbered starting from 0 — Status.Pending is 0, Status.Active is 1, and so on. Status[current] looks the number back up to its name.

String enums

A string enum gives each member an explicit string value instead, which is often clearer when you might log or serialize the value somewhere.

enum Direction {
  Up = "UP",
  Down = "DOWN",
  Left = "LEFT",
  Right = "RIGHT",
}

let move: Direction = Direction.Left;
console.log(move);

LEFT

Next: classes and objects — bundling data and behavior together, with TypeScript's access modifiers.