> 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/types.md).

# Types

Types in TypeScript allow you to define custom data structures and enforce specific constraints on the data. They are similar to interfaces but offer additional features.

**Example Type**:

```typescript
type User = {
    firstName: string;
    lastName: string;
    age: number;
};
```

**1. Unions**

Unions allow you to specify that a value can be one of several types. This is useful when a variable or parameter can accept multiple data types.

**Example**:

```typescript
type StringOrNumber = string | number;

function printId(id: StringOrNumber) {
    console.log(`ID: ${id}`);
}

printId(101);     // Output: ID: 101
printId("202");   // Output: ID: 202
```

**2. Intersection**

Intersection types combine multiple types into one. This allows you to create a type that has all properties of the individual types.

**Example**:

```typescript
type Employee = {
    name: string;
    startDate: Date;
};

type Manager = {
    name: string;
    department: string;
};

type TeamLead = Employee & Manager;

const teamLead: TeamLead = {
    name: "harkirat",
    startDate: new Date(),
    department: "Software developer"
};
```

In this example, `TeamLead` is an intersection of `Employee` and `Manager`, meaning it must have all properties defined in both types.

**3. Type Aliases**

Type aliases allow you to create custom names for types, making your code more readable and maintainable.

**Example**:

```typescript
type Point = {
    x: number;
    y: number;
};

type Rectangle = {
    topLeft: Point;
    bottomRight: Point;
};

const rect: Rectangle = {
    topLeft: { x: 0, y: 0 },
    bottomRight: { x: 10, y: 10 }
};
```

**4. Literal Types**

Literal types allow you to specify exact values that a variable can have.

**Example**:

```typescript
type Color = "red" | "green" | "blue";

function printColor(color: Color) {
    console.log(`Selected color: ${color}`);
}

printColor("red");   // Output: Selected color: red
```

**Summary**

* Types in TypeScript allow you to define custom data structures and enforce specific constraints on the data.
* Unions and intersections provide flexibility in specifying variable types and combining multiple types.
* Type aliases improve code readability by creating custom names for complex types.
* Literal types allow you to specify exact values that variables can have, enhancing type safety and expressiveness in your code.