Getting Started with Express Js: Sigma Web Development Course Tutorial #88

In this tutorial, we will be learning about Express.js, which is a popular Node.js framework for building web applications. Express.js provides a simple and flexible way to build web servers and handle HTTP requests. It is widely used in the industry for building APIs and web applications.

Express.js is known for its simplicity and ease of use. It is built on top of Node.js and provides a minimalist and unopinionated structure for building web servers. This allows developers to have more control over their code and build applications according to their own preferences.

To get started with Express.js, you will need to have Node.js installed on your machine. You can download Node.js from the official website and follow the installation instructions. Once you have Node.js installed, you can create a new project folder and run the following command to initialize a new Node.js project:

npm init -y

This will create a package.json file in your project folder, which will store information about your project and its dependencies. Next, you will need to install Express.js as a dependency for your project. You can do this by running the following command:

npm install express

This will install Express.js in your project folder and add it as a dependency in your package.json file. You can now start writing your Express.js application by creating a new JavaScript file, for example, app.js, and require Express.js in it:

const express = require('express');
const app = express();

In the above code, we first require the express module and create an instance of the express application by calling express(). This creates a new Express.js application that we can use to define routes, handle requests, and set up middleware.

Next, we can define a route in our application by using the app.get() method. This method takes two arguments: the path of the route and a callback function that is called when a request is made to that route. For example, we can define a simple route that responds with "Hello, World!" when a GET request is made to the root path /:

app.get('/', (req, res) => {
  res.send('Hello, World!');
});

In the above code, we define a route for the root path / using the app.get() method. The callback function takes two arguments, req (the request object) and res (the response object). We use the res.send() method to send a response with the text "Hello, World!".

Finally, we need to start the server and listen for incoming requests. We can do this by calling the app.listen() method and specifying the port number on which the server should listen. For example, we can start the server on port 3000:

app.listen(3000, () => {
  console.log('Server started on http://localhost:3000');
});

In the above code, we call the app.listen() method and pass the port number 3000 as an argument. We also provide a callback function that will be executed once the server is started. In this function, we log a message to the console indicating that the server has started and is listening on http://localhost:3000.

To run your Express.js application, you can use the following command:

node app.js

This will start the server and you can access your web application by opening http://localhost:3000 in your browser. You should see the message "Hello, World!" displayed on the screen.

This is just a basic introduction to Express.js and there is much more to learn about this powerful framework. In future tutorials, we will cover more advanced topics such as routing, middleware, templates, and database integration with Express.js. Express.js is a powerful framework for building web applications and APIs, and it is widely used in the industry for its simplicity and flexibility.