Worth noting that if you'd prefer to use interfaces over types (although they're largely similar) that you can typically use [**interface extension**][3] instead of [**type intersection**][2] like this:

```ts
// base type
interface Shape {
  color: string;
}

// extension
interface Square extends Shape {
  sideLength: number;
}

// intersection
type Square = Shape & {
  sideLength: number;
}
```

**See Also**: [Difference between extending and intersecting interfaces in TypeScript?][1]

[1]: https://stackoverflow.com/q/52681316/1366033
[2]: https://www.typescriptlang.org/docs/handbook/2/objects.html#intersection-types
[3]: https://www.typescriptlang.org/docs/handbook/interfaces.html#extending-interfaces

I'm struggling to find the definition of the `&` operator in TypeScript. I have recently come across the following code:



    type IRecord<T> = T & TypedMap<T>;

What does that operator do, and how is it different from the union type `|`?

Typescript & operator

Answer