Course Content
Node.js Express: API & CLI Apps
Node.js Express: API & CLI Apps
Setting up an Express App
Let's create our first backend app with Express.js. Are you ready to get started?
Installing Express.js
Create a new directory for the app, and open the folder in the code editor. We are ready to start. In the terminal, run this command:
It's like ordering Express.js from a virtual app store, and npm is our delivery service.
As a result, we get such file-folder structure of our app:
Basic project structure:
node_modules
- Contains installed packages;package.json
andpackage-lock.json
- List project dependencies and scripts;app.js
orindex.js
- Entry point for the Express application. We create it manually by ourselves.
🏗️ Build First Express App
Create a simple web server using Node.js and the Express.js framework. Follow the following steps:
Step 1: Import Express
As library we need firstly to import it to our file:
Step 2: Creating an Express Application Instance
We create an instance of the Express application. This app
variable will be used to configure and define the web server's behavior.
Step 3: Set the Port
We define the port number that our server will listen on. In this case, it's set to 3000, but we can choose any available port number.
Step 4: Defining a Route
We set up a route for handling HTTP GET requests to the root URL (/
). When a client (typically a web browser) accesses the server's root URL, it responds with Hello, World!
.
app.get('/')
- This defines a route for handling GET requests to the root path (/
). We can define routes for different HTTP methods (GET, POST, PUT, DELETE, etc.);(req, res) => { ... }
- This is a callback function that gets executed when a client makes a GET request to the specified route. It takes two arguments:req
(the request object) andres
(the response object). In this case, it simply sends theHello, World!
text as the response.
Step 5: Start the Server
Let's start the server and make it listen on the specified port (in our case, port 3000). When the server is successfully started, it logs a message to the console, indicating which port it is listening on.
app.listen(port, ...)
- This method starts the server and listens on the specified port. The second argument is a callback function that gets executed once the server is up and running.
Step 6: Run the App
We run the app in the terminal using node
command.
🌐 After running the script
Our server will be running, and we can access it by opening a web browser and navigating to http://localhost:3000
. You should see Hello, World!
displayed in your browser.
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