My Blog

Category: 01. Express Js

https://ajeetchaulagain.com/static/7cb4af597964b0911fe71cb2f8148d64/87351/express-js.png

  • Using External Middleware

    Express can use various middleware for functionalities like authentication, logging, etc. For example, to use the morgan logging library:

    npm install morgan

    Then, in app.js:

    const morgan = require('morgan');
app.use(morgan('dev'));

  • Serving Static Files

    To serve static files like HTML, CSS, and JavaScript, use:

    app.use(express.static('public'));

    Create a public directory and put your static files there.

  • Error Handling

    Add an error handling middleware to catch and respond to errors:

    app.use((err, req, res, next) => {
  console.error(err.stack);
  res.status(500).send('Something broke!');
});

  • Adding More Routes

    You can add more routes to handle different URLs and HTTP methods. For example:

    // Route for a user profile page
app.get('/user/:id', (req, res) => {
  const userId = req.params.id;
  res.send(User profile for user ID: ${userId});
});

  • Understanding the Code

    • const express = require('express');: Imports the Express module.
    • const app = express();: Creates an Express application.
    • app.use(express.json());: Adds middleware to parse JSON request bodies.
    • app.get('/', (req, res) => {...});: Defines a route that handles GET requests to the root URL.
    • app.post('/data', (req, res) => {...});: Defines a route that handles POST requests to /data.
    • app.listen(port, () => {...});: Starts the server and listens on the specified port.

  • Run Your Application

    Start your server using Node.js:

    codenode app.js

    Visit http://localhost:3000 in your browser to see “Hello World!” and use a tool like Postman or curl to test the /data POST endpoint.

  • Create Your First Express Application

    Create a file named app.js (or index.js) in your project directory and add the following code:

    const express = require('express');
const app = express();
const port = 3000;

// Middleware to handle JSON body
app.use(express.json());

// Route for the home page
app.get('/', (req, res) => {
  res.send('Hello World!');
});

// Route to handle POST requests
app.post('/data', (req, res) => {
  res.json({

    receivedData: req.body
      });
});

// Start the server
app.listen(port, () => {
  console.log(Server is running on http://localhost:${port});
});

  • Install Express.js

    Install Express.js using npm.

    codenpm install express

  • Initialize a New Node.js Project

    Run the following command to create a package.json file, which will manage your project’s dependencies.

    codenpm init -y

  • Setup Your Environment

    a. Install Node.js

    Download and install Node.js from nodejs.org. This will include npm (Node Package Manager), which you’ll use to manage packages.

    b. Create a Project Directory

    codemkdir my-express-app
cd my-express-app