Learn to Build a Simple, yet Powerful Web Server with Typescript and Koa

Learn how to build a simple web server using Typescript and Koa in this comprehensive tutorial. Follow along and take your backend development skills to the next level with this powerful combination of technologies.

Learn to Build a Simple, yet Powerful Web Server with Typescript and Koa
Photo by Kym Ellis / Unsplash
Dive into Node.js Backend Development: Part 1 — Handling Your First HTTP Request

Ready to take your web development skills to the next level and build your own custom web servers? Look no further! In this tutorial, I’ll walk you through the process of creating a simple HTTP request-handling project using the powerful combination of Typescript and Koa.

But first, why choose Typescript? It is the third most loved language by developers and has numerous benefits that make it worth considering. For one, it helps you write safer and more reliable code by enforcing strong type-checking. It also makes collaborating with others more accessible and faster, thanks to its straightforward and structured syntax. Many IDEs have excellent integration with Typescript, providing helpful suggestions and linting checks as you code.

As for Koa, it’s a lightweight framework that makes it easy to understand the flow of your server and clearly organize your logic. It also integrates seamlessly with the latest Javascript features, including native async support. And because it only does a little for you behind the scenes, it encourages you to learn and understand the core concepts of Node.js and backend development.

So let’s get started building your first web server with Typescript and Koa! 🎉

Let’s begin!

… with the basics. The following steps require nodejs and npm to be already installed.

You’ll want to run the npm init command to get started on your new repository. It will prompt you to provide some information about your project, and then it will create a package.json file for you.

Once npm init is finished, you can install the packages you need for your project. In the example provided, you’re installing some packages twice: once for the package itself and once for the @types/package version.

The @types/package version installs the Typescript interfaces for the corresponding package. These interfaces provide type definitions for all the methods and variables in the package, which enables strong type-checking in your code.

So, to summarize, the npm init command sets up your project and creates a package.json file. Then you can install the necessary packages, including any @types/package versions, for added type-checking support.

Using node with typescript

Node.js does not natively support Typescript, so we’ll need to use a package called ts-node to convert our Typescript code to Javascript at runtime. To test this out, let’s create a simple “Hello World” file called server.ts.

If you try running the file with node server.ts, you may encounter an error. This is because we need to set up a script in our package.json file to use the ts-node package. You’ll need to have installed the ts-node package to do this.

Once you’ve set up the script, you can run your Typescript code using npm start. If everything is set up correctly, you should see “Hello World” message printed on the console 😃

Finally, it’s a good idea to create a .gitignore file to prevent any unwanted files from being committed to your repository. This will help keep your codebase clean from node temporary files.

Handle the first request — koa

Next, we’ll introduce the Koa framework, which will help us structure our request-handling logic. Essentially, when a user makes an HTTP request to our server, Koa helps us process the request and generate a response.

For example, the following snippet of a GET / request returns the message Hello World! :

One thing to note is that Koa only handles the basic request and response flow. If you want to do anything more advanced, like handling request bodies or routing requests to different functions, you’ll need to set it up yourself (in this case, we’re using the koa-router package to handle routing). Other frameworks, like Express, come with these features bundled in, but using Koa gives you a chance to understand the core concepts of the web more deeply 😉

Another critical concept to understand is the app.use() method, which allows you to chain custom methods for each route, or at higher levels.

These methods are called “middlewares”, and they modify a “context” object that gets passed along until the final method, called the “controller” (in this case, the helloWorldController function from above).

When the controller function finishes executing, the HTTP response is sent back to the user.

In the example code snippet, we’re using Koa to handle a GET request to the home route (/) and returning a simple “Hello World” message. I hope this helps clarify how Koa works and how it fits into the overall request-response flow of a web server.

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