> For the complete documentation index, see [llms.txt](https://jorgedacostaza.gitbook.io/typescript-pt/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://jorgedacostaza.gitbook.io/typescript-pt/type-system/intro/variables.md).

# Variables

For example to tell TypeScript about the [`process` variable](https://nodejs.org/api/process.html) you *can* do:

```typescript
declare var process: any;
```

> You don't *need* to do this for `process` as there is already a [community maintained `node.d.ts`](https://github.com/DefinitelyTyped/DefinitelyTyped/blob/master/types/node/index.d.ts).

This allows you to use the `process` variable without TypeScript complaining:

```typescript
process.exit();
```

We recommend using an interface wherever possible e.g.:

```typescript
interface Process {
    exit(code?: number): void;
}
declare var process: Process;
```

This allows other people to *extend* the nature of these global variables while still telling TypeScript about such modifications. E.g. consider the following case where we add an `exitWithLogging` function to process for our amusement:

```typescript
interface Process {
    exitWithLogging(code?: number): void;
}
process.exitWithLogging = function() {
    console.log("exiting");
    process.exit.apply(process, arguments);
};
```

Let's look at interfaces in a bit more detail next.