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HTML / CSS / JS

// Const enum — values are inlined, no runtime object
const enum Weekday {
    Monday = 1,
    Tuesday,
    Wednesday,
    Thursday,
    Friday,
}

const day: Weekday = Weekday.Wednesday; // compiled to: const day = 3;

// POJO enum pattern — avoids const enum pitfalls
const Color = {
    Red:   "RED",
    Green: "GREEN",
    Blue:  "BLUE",
} as const;

type Color = typeof Color[keyof typeof Color]; // "RED" | "GREEN" | "BLUE"

function paintWall(color: Color): void {
    console.log(`Painting with ${color}`);
}

paintWall(Color.Red);  // OK
// paintWall("PURPLE"); // Error

// Iterating over an enum
enum Permission {
    Read  = "READ",
    Write = "WRITE",
    Admin = "ADMIN",
}

const allPermissions = Object.values(Permission);
// ["READ", "WRITE", "ADMIN"]

// Enum bitflags (numeric)
const enum FileMode {
    None    = 0,
    Read    = 1 << 0, // 1
    Write   = 1 << 1, // 2
    Execute = 1 << 2, // 4
}

const mode = FileMode.Read | FileMode.Write; // 3
const canRead  = (mode & FileMode.Read)  !== 0; // true
const canExec  = (mode & FileMode.Execute) !== 0; // false