Literal Types & Enums

Literal Types

A literal type is the exact value of a primitive.

type YesNo = "yes" | "no";
let answer: YesNo = "yes"; // OK

Numeric Literal Types

type OneToThree = 1 | 2 | 3;
let n: OneToThree = 2;

Enums

Enumerations provide a named set of values.

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

let dir: Direction = Direction.Up;

Const enums (inlined at compile time)

const enum Color { Red, Green, Blue }
let c = Color.Green; // emitted as 1