Express.js is a minimal and flexible Node.js web application framework that provides a robust set of features for web and mobile applications. It simplifies the process of building server-side applications using Node.js. This means handles requests from the client, processes data, and sends responses back.
- Simplicity: It provides a streamlined way to handle HTTP requests and responses.
- Routing: It helps define different routes for your application, like different pages or API endpoints.
- Middleware: It allows you to add custom functions (middleware) to process requests and responses.
When we start an Express.js server, it listens on a specified port for incoming HTTP requests. The server is usually run on localhost during development to test the application. Look into HTTP requests to learn about the basic requests a server deals with. All data from the HTML to server is usually done through HTML forms. These HTTP concepts are fundamental before moving onto next portion.
The following code handles the GET request to the root URL (simply contains "/" without anything being followed).
app.get(”/”):
- Sets up an HTTP GET route for the root URL (”/”).
- When a client sends a GET request to the root URL, this route is triggered.
(req, res) => {…}:
Callback function that handles the request and response.
- req: Represents the incoming request object.
- res: Represents the outgoing response object.
Details on (req, res) is at Request and Response in Express . Check arrow function for this type of function definition style.
const app = express();
app.get("/", (req,res) => {
console.log(req);
res.sendFile("index.html")
});In most node apps, express is used to simplify the backend dealings, and there is a particular way to retrieve current local file path in Node applications. In general, node applications follow a specific file structure as mentioned in File Structure for a Node.js Application.
Move to 1 - 1-Basics of express and backend after this intro page.