Node.js is a popular platform for developing backend applications and web services. Using TypeScript in Node.js enhances the development experience by adding static typing, autocompletion, and error checking during development time. In this chapter, we will learn how to set up a Node.js project with TypeScript and how to use TypeScript to develop secure and scalable backend applications.

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Setting Up a Node.js Project with TypeScript

To start, you need to initialize a Node.js project with support for TypeScript. First, create a folder for the project and run the following command to initialize npm:

bash

Installing TypeScript and Node Types

Then, install TypeScript and the type definitions for Node.js using npm:

bash

Setting Up the tsconfig.json File

After installing TypeScript, you need to set up the tsconfig.json file to define how TypeScript code should be compiled in Node.js. Run the following command to generate the tsconfig.json file:

bash

Next, edit the tsconfig.json file to ensure it is correctly configured for Node.js:

json

Creating a Server with TypeScript

Once the project is set up, we can create a basic server using TypeScript and Node.js APIs.

Example of an HTTP Server with TypeScript

Create a file named index.ts in the src folder and write the following code to create a basic HTTP server:

typescript

Compiling and Running the Server

To compile the TypeScript code, execute the following command:

bash

Then, you can run the server using Node.js:

bash

Using Express with TypeScript

Express is one of the most widely used frameworks for building web applications and APIs in Node.js. With TypeScript, we can correctly type the controllers and middlewares of Express, which helps us avoid common errors.

Installing Express and Express Types

First, install Express and the corresponding type definitions:

bash

Example of an Express Server with TypeScript

Next, create a file server.ts in the src folder and write the following code to create an Express server with TypeScript:

typescript

Typing Request Parameters in Express

With TypeScript, we can type the parameters of a request to ensure we are handling the data correctly. Here is an example of how to do it with a route that receives dynamic parameters:

typescript

Typing Middlewares in Express

Middlewares in Express can benefit from TypeScript typing, making it easier to create reusable and secure middlewares.

Example of Middleware with TypeScript

typescript

Conclusion

In this chapter, we learned how to configure and develop Node.js applications with TypeScript. We saw how to set up a basic HTTP server, how to integrate Express with TypeScript, and how to leverage static typing in controllers and middlewares. TypeScript in Node.js provides a safer and more productive development experience.