Enumerations (Enums)

An enum is a special class that represents a group of pre-defined constants. It allows developers to define a set of named constraints, making the code much more readable and preventing simple typographical strings from dominating the logical systems.

Numeric Enums

By default, Enums initialize the very first item to the number 0 and auto-increment up.

enum Direction {
    Up,     // Value is 0
    Down,   // Value is 1
    Left,   // Value is 2
    Right   // Value is 3
}

// Accessing the enum state
let move: Direction = Direction.Up;

console.log(move); // 0

You can optionally manually set the starter number!

enum ResponseCodes {
    NotFound = 404,
    Success = 200,
    ServerCrash = 500
}

String Enums

Strictly locking strings is often safer and more readable during active network debugging than trying to figure out what numeric 0 translates to.

enum Role {
    Admin = "ADMIN",
    Editor = "EDITOR",
    Viewer = "VIEWER"
}

// In the database or parameters, we enforce one of these string types!
function assignRole(userRole: Role) {
    if(userRole === Role.Admin) {
        console.log("Full Authority Checked.");
    }
}

assignRole(Role.Editor);