---
title: "add types to a javascript when using typescript"
date: 2021-07-12T11:12:32+02:00
draft: false
snippet_types:
- js
- typescript
---

Today I had a .js file that I needed to import into the rest of a TypeScript app but could not convert it to a .ts file. To get around this limitation I added an accompanying .d.ts file. 


countryConfig.js

```js
const countries = [
    {
        code: 'de',
        domainExtension: '.de'
    },
    ...
];

exports.countries = countries;
```

countryConfig.d.ts

```typescript
interface Country {
    code: string;
    domainExtension: string;
}

export const countries: Array<Country>;
```

app.ts

```typescript
import countries from './countryConfig'

...
```

source: https://www.typescriptlang.org/docs/handbook/declaration-files/templates/module-d-ts.html