> For the complete documentation index, see [llms.txt](https://docs.bashschool.in/v1/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.bashschool.in/v1/javascript/typescript/enums.md).

# Enums

Enums (short for enumerations) in TypeScript are a feature that allows you to define a set of named constants. They provide a human-readable way to represent a set of constant values, which might otherwise be represented as numbers or strings.

**Example 1: Game Controls**

Let’s say you have a game where you have to perform an action based on whether the user has pressed the up, down, left, or right arrow key.

```typescript
enum Direction {
    Up,
    Down,
    Left,
    Right
}

function doSomething(keyPressed: Direction) {
    // do something.
}

doSomething(Direction.Up);
```

This makes the code cleaner and easier to understand. At runtime, the values stored are still numbers (0, 1, 2, 3).

**2. Runtime Values of Enums**

Let's log the runtime value of `Direction.Up`:

```typescript
console.log(Direction.Up); // Output: 0
```

By default, enums get values starting from 0 and incrementing by 1 for each subsequent member.

**3. Customizing Enum Values**

You can customize the values of enums:

```typescript
enum Direction {
    Up = 1,
    Down,   // 2
    Left,   // 3
    Right   // 4
}

function doSomething(keyPressed: Direction) {
    // do something.
}

doSomething(Direction.Down);
```

**4. Using String Values**

Enums can also be represented as strings:

```typescript
enum Direction {
    Up = "UP",
    Down = "Down",
    Left = "Left",
    Right = "Right"
}

function doSomething(keyPressed: Direction) {
    // do something.
}

doSomething(Direction.Down);
```

**5. Common Use Case in Express**

Enums are commonly used in frameworks like Express to represent status codes:

```typescript
enum ResponseStatus {
    Success = 200,
    NotFound = 404,
    Error = 500
}

app.get("/", (req, res) => {
    if (!req.query.userId) {
        res.status(ResponseStatus.Error).json({});
    }
    // and so on...
    res.status(ResponseStatus.Success).json({});
});
```

Enums provide a convenient way to define a set of related constants and improve code readability and maintainability. They are widely used in various scenarios, including game development, web frameworks, and API development.