Building a Type-Safe API with TypeScript and Express

## Introduction

TypeScript has become an essential tool for JavaScript developers who want to add static type checking to their projects. When building APIs with Express, TypeScript can help catch errors early and provide better documentation for your endpoints.

## Setting Up Your Project

First, let's initialize a new TypeScript project:

```bash
npm init -y
npm install express
npm install -D typescript @types/express @types/node
```

Create a `tsconfig.json` file:

```json
{
"compilerOptions": {
"target": "es2016",
"module": "commonjs",
"outDir": "./dist",
"strict": true,
"esModuleInterop": true
},
"include": ["src/**/*"]
}
```

## Creating Type-Safe Routes

One of the benefits of using TypeScript with Express is the ability to define interfaces for your request and response objects:

```typescript
interface User {
id: string;
name: string;
email: string;
}

app.get('/users/:id', (req, res) => {
const userId = req.params.id;
const user: User = getUserById(userId);

if (!user) {
return res.status(404).json({ message: 'User not found' });
}

return res.json(user);
});
```

## Conclusion

By adding TypeScript to your Express API, you gain the benefits of static type checking, better IDE support, and more maintainable code. This approach helps catch errors during development rather than at runtime, leading to more robust applications.