Enums

Enums give names to sets of related values. Instead of using magic strings or numbers, you use meaningful identifiers.
enum Status {
	Pending = 'pending',
	Active = 'active',
	Completed = 'completed',
}

const orderStatus: Status = Status.Active

String Enums vs Numeric Enums

// String enum - values are strings
enum Color {
	Red = 'red',
	Green = 'green',
	Blue = 'blue',
}

// Numeric enum - values are numbers (auto-incremented)
enum Direction {
	Up, // 0
	Down, // 1
	Left, // 2
	Right, // 3
}

Enums vs Union Types

TypeScript offers an alternative: union types of string literals.
// Enum
enum Status {
	Pending = 'pending',
	Active = 'active',
}

// Union type alternative
type Status = 'pending' | 'active'
Many TypeScript developers prefer union types because:
  • Simpler syntax
  • No runtime overhead
  • Better tree-shaking
  • Works with string literals directly
In functional programming, union types are the standard way to represent a fixed set of possibilities. They work seamlessly with TypeScript's type narrowing and discriminated unionsβ€”patterns you'll use extensively in modern React and other functional codebases.
Choose enums when you need reverse mapping (number β†’ name) or when working with teams that prefer the enum syntax. Otherwise, union types are often the better choice.
In this exercise, you'll work with both enums and union types.
EditStart Learning