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Nadim Chowdhury
Nadim Chowdhury

Posted on • Edited on

How to learn Express JS?

Learning Express.js can be a rewarding experience as it is a minimal and flexible Node.js web application framework that provides a robust set of features for building web and mobile applications. Here's a structured guide to help you get started with Express.js:

Step 1: Understand the Basics of Node.js

Before diving into Express.js, make sure you have a solid understanding of Node.js.

  1. Node.js Basics:
    • Understand the event-driven architecture.
    • Learn how to create a basic server using Node.js.
    • Familiarize yourself with asynchronous programming using callbacks, promises, and async/await.

Step 2: Set Up Your Development Environment

  1. Install Node.js:
    Download and install Node.js from nodejs.org.

  2. Initialize a New Node.js Project:
    Create a new directory for your project and initialize it with npm.

   mkdir my-express-app
   cd my-express-app
   npm init -y
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  1. Install Express.js:
   npm install express
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Step 3: Create a Simple Express.js Server

  1. Create the Server: Create an index.js file in your project directory.
   const express = require('express');
   const app = express();
   const port = 3000;

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

   app.listen(port, () => {
     console.log(`Server is running at http://localhost:${port}`);
   });
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  1. Run the Server:
   node index.js
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Open your browser and navigate to http://localhost:3000. You should see "Hello, Express!".

Step 4: Learn the Basics of Express.js

  1. Routing: Express uses routing to determine how an application responds to a client request.
   app.get('/hello', (req, res) => {
     res.send('Hello World!');
   });

   app.post('/hello', (req, res) => {
     res.send('Got a POST request');
   });

   app.put('/hello', (req, res) => {
     res.send('Got a PUT request');
   });

   app.delete('/hello', (req, res) => {
     res.send('Got a DELETE request');
   });
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  1. Middleware: Middleware functions are functions that have access to the request object, the response object, and the next middleware function in the application’s request-response cycle.
   app.use((req, res, next) => {
     console.log('Time:', Date.now());
     next();
   });
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  1. Serving Static Files: Express can serve static files, such as images, CSS, and JavaScript.
   app.use(express.static('public'));
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Step 5: Create a RESTful API

Let's create a simple RESTful API to manage a list of users.

  1. Set Up a Basic Structure: Create a new directory for routes and a file for the users route.
   mkdir routes
   touch routes/users.js
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  1. Define Routes for Users: Open routes/users.js and define the routes.
   const express = require('express');
   const router = express.Router();

   let users = [
     { id: 1, name: 'John Doe' },
     { id: 2, name: 'Jane Smith' },
   ];

   // Get all users
   router.get('/', (req, res) => {
     res.json(users);
   });

   // Get a user by ID
   router.get('/:id', (req, res) => {
     const user = users.find(u => u.id === parseInt(req.params.id));
     if (!user) return res.status(404).send('User not found');
     res.json(user);
   });

   // Create a new user
   router.post('/', (req, res) => {
     const user = {
       id: users.length + 1,
       name: req.body.name,
     };
     users.push(user);
     res.status(201).json(user);
   });

   // Update a user
   router.put('/:id', (req, res) => {
     const user = users.find(u => u.id === parseInt(req.params.id));
     if (!user) return res.status(404).send('User not found');
     user.name = req.body.name;
     res.json(user);
   });

   // Delete a user
   router.delete('/:id', (req, res) => {
     const userIndex = users.findIndex(u => u.id === parseInt(req.params.id));
     if (userIndex === -1) return res.status(404).send('User not found');
     users.splice(userIndex, 1);
     res.status(204).send();
   });

   module.exports = router;
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  1. Use the Users Route in Your App: Open index.js and use the users route.
   const express = require('express');
   const app = express();
   const port = 3000;
   const usersRouter = require('./routes/users');

   app.use(express.json()); // for parsing application/json

   app.use('/users', usersRouter);

   app.listen(port, () => {
     console.log(`Server is running at http://localhost:${port}`);
   });
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  1. Test the API: Use a tool like Postman or curl to test the API endpoints.

Step 6: Learn More Advanced Express.js Features

  1. Error Handling: Middleware for handling errors.
   app.use((err, req, res, next) => {
     console.error(err.stack);
     res.status(500).send('Something broke!');
   });
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  1. Templating Engines: Use templating engines like Pug or EJS for rendering dynamic HTML pages.
   npm install pug
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   app.set('view engine', 'pug');

   app.get('/', (req, res) => {
     res.render('index', { title: 'Hey', message: 'Hello there!' });
   });
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  1. Database Integration:
    Connect your application to a database like MongoDB or PostgreSQL.

    • For MongoDB, use Mongoose:
     npm install mongoose
    
   const mongoose = require('mongoose');

   mongoose.connect('mongodb://localhost/mydatabase', {
     useNewUrlParser: true,
     useUnifiedTopology: true,
   });

   const userSchema = new mongoose.Schema({
     name: String,
   });

   const User = mongoose.model('User', userSchema);

   app.post('/users', async (req, res) => {
     const user = new User({ name: req.body.name });
     await user.save();
     res.status(201).json(user);
   });
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Step 7: Testing and Debugging

  1. Unit Testing: Use Mocha and Chai for unit testing.
   npm install mocha chai
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   const chai = require('chai');
   const chaiHttp = require('chai-http');
   const server = require('../index');

   chai.should();
   chai.use(chaiHttp);

   describe('Users API', () => {
     it('should get all users', (done) => {
       chai.request(server)
         .get('/users')
         .end((err, res) => {
           res.should.have.status(200);
           res.body.should.be.a('array');
           done();
         });
     });
   });
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  1. End-to-End Testing: Use Supertest for end-to-end testing.
   npm install supertest
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   const request = require('supertest');
   const app = require('../index');

   describe('GET /users', () => {
     it('responds with json', (done) => {
       request(app)
         .get('/users')
         .set('Accept', 'application/json')
         .expect('Content-Type', /json/)
         .expect(200, done);
     });
   });
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Step 8: Learning Resources

  1. Official Documentation:

  2. Online Courses:

  3. Books:

    • "Express.js Guide" by Azat Mardan
  4. Tutorials and Articles:

  5. Community and Forums:

Step 9: Build Real-World Projects

  1. Choose Real-World Projects:

    • Build applications like a blog, e-commerce site, or social media app.
  2. Contribute to Open Source:

    • Contribute to open source Express.js projects on GitHub.

Step 10: Stay Updated

  1. Follow Node.js and Express.js Updates:
    • Follow the Node.js blog
    • Join Node.js and Express.js newsletters
    • Attend Node.js and Express.js conferences and meetups

By following this structured guide and practicing regularly, you'll build up your knowledge and skills in Express.js, enabling you to create powerful and efficient server-side applications. If you have any specific questions or need further details on any step, feel free to ask!

Sure! Let's dive into learning Express.js, a popular Node.js framework for building web and mobile applications. Here's a step-by-step guide to help you get started with Express.js:

Step 1: Set Up Your Development Environment

  1. Install Node.js:
    Download and install Node.js from nodejs.org.

  2. Initialize a New Node.js Project:
    Create a new directory for your project and initialize it with npm.

   mkdir my-express-app
   cd my-express-app
   npm init -y
Enter fullscreen mode Exit fullscreen mode
  1. Install Express.js:
   npm install express
Enter fullscreen mode Exit fullscreen mode

Step 2: Create a Simple Express.js Server

  1. Create the Server: Create an index.js file in your project directory.
   const express = require('express');
   const app = express();
   const port = 3000;

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

   app.listen(port, () => {
     console.log(`Server is running at http://localhost:${port}`);
   });
Enter fullscreen mode Exit fullscreen mode
  1. Run the Server:
   node index.js
Enter fullscreen mode Exit fullscreen mode

Open your browser and navigate to http://localhost:3000. You should see "Hello, Express!".

Step 3: Learn the Basics of Express.js

  1. Routing: Express uses routing to determine how an application responds to a client request.
   app.get('/hello', (req, res) => {
     res.send('Hello World!');
   });

   app.post('/hello', (req, res) => {
     res.send('Got a POST request');
   });

   app.put('/hello', (req, res) => {
     res.send('Got a PUT request');
   });

   app.delete('/hello', (req, res) => {
     res.send('Got a DELETE request');
   });
Enter fullscreen mode Exit fullscreen mode
  1. Middleware: Middleware functions are functions that have access to the request object, the response object, and the next middleware function in the application’s request-response cycle.
   app.use((req, res, next) => {
     console.log('Time:', Date.now());
     next();
   });
Enter fullscreen mode Exit fullscreen mode
  1. Serving Static Files: Express can serve static files, such as images, CSS, and JavaScript.
   app.use(express.static('public'));
Enter fullscreen mode Exit fullscreen mode

Step 4: Create a RESTful API

Let's create a simple RESTful API to manage a list of users.

  1. Set Up a Basic Structure: Create a new directory for routes and a file for the users route.
   mkdir routes
   touch routes/users.js
Enter fullscreen mode Exit fullscreen mode
  1. Define Routes for Users: Open routes/users.js and define the routes.
   const express = require('express');
   const router = express.Router();

   let users = [
     { id: 1, name: 'John Doe' },
     { id: 2, name: 'Jane Smith' },
   ];

   // Get all users
   router.get('/', (req, res) => {
     res.json(users);
   });

   // Get a user by ID
   router.get('/:id', (req, res) => {
     const user = users.find(u => u.id === parseInt(req.params.id));
     if (!user) return res.status(404).send('User not found');
     res.json(user);
   });

   // Create a new user
   router.post('/', (req, res) => {
     const user = {
       id: users.length + 1,
       name: req.body.name,
     };
     users.push(user);
     res.status(201).json(user);
   });

   // Update a user
   router.put('/:id', (req, res) => {
     const user = users.find(u => u.id === parseInt(req.params.id));
     if (!user) return res.status(404).send('User not found');
     user.name = req.body.name;
     res.json(user);
   });

   // Delete a user
   router.delete('/:id', (req, res) => {
     const userIndex = users.findIndex(u => u.id === parseInt(req.params.id));
     if (userIndex === -1) return res.status(404).send('User not found');
     users.splice(userIndex, 1);
     res.status(204).send();
   });

   module.exports = router;
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  1. Use the Users Route in Your App: Open index.js and use the users route.
   const express = require('express');
   const app = express();
   const port = 3000;
   const usersRouter = require('./routes/users');

   app.use(express.json()); // for parsing application/json

   app.use('/users', usersRouter);

   app.listen(port, () => {
     console.log(`Server is running at http://localhost:${port}`);
   });
Enter fullscreen mode Exit fullscreen mode
  1. Test the API: Use a tool like Postman or curl to test the API endpoints.

Step 5: Learn More Advanced Express.js Features

  1. Error Handling: Middleware for handling errors.
   app.use((err, req, res, next) => {
     console.error(err.stack);
     res.status(500).send('Something broke!');
   });
Enter fullscreen mode Exit fullscreen mode
  1. Templating Engines: Use templating engines like Pug or EJS for rendering dynamic HTML pages.
   npm install pug
Enter fullscreen mode Exit fullscreen mode
   app.set('view engine', 'pug');

   app.get('/', (req, res) => {
     res.render('index', { title: 'Hey', message: 'Hello there!' });
   });
Enter fullscreen mode Exit fullscreen mode
  1. Database Integration:
    Connect your application to a database like MongoDB or PostgreSQL.

    • For MongoDB, use Mongoose:
     npm install mongoose
    
   const mongoose = require('mongoose');

   mongoose.connect('mongodb://localhost/mydatabase', {
     useNewUrlParser: true,
     useUnifiedTopology: true,
   });

   const userSchema = new mongoose.Schema({
     name: String,
   });

   const User = mongoose.model('User', userSchema);

   app.post('/users', async (req, res) => {
     const user = new User({ name: req.body.name });
     await user.save();
     res.status(201).json(user);
   });
Enter fullscreen mode Exit fullscreen mode

Step 6: Testing and Debugging

  1. Unit Testing: Use Mocha and Chai for unit testing.
   npm install mocha chai
Enter fullscreen mode Exit fullscreen mode
   const chai = require('chai');
   const chaiHttp = require('chai-http');
   const server = require('../index');

   chai.should();
   chai.use(chaiHttp);

   describe('Users API', () => {
     it('should get all users', (done) => {
       chai.request(server)
         .get('/users')
         .end((err, res) => {
           res.should.have.status(200);
           res.body.should.be.a('array');
           done();
         });
     });
   });
Enter fullscreen mode Exit fullscreen mode
  1. End-to-End Testing: Use Supertest for end-to-end testing.
   npm install supertest
Enter fullscreen mode Exit fullscreen mode
   const request = require('supertest');
   const app = require('../index');

   describe('GET /users', () => {
     it('responds with json', (done) => {
       request(app)
         .get('/users')
         .set('Accept', 'application/json')
         .expect('Content-Type', /json/)
         .expect(200, done);
     });
   });
Enter fullscreen mode Exit fullscreen mode

Step 7: Learning Resources

  1. Official Documentation:

  2. Online Courses:

  3. Books:

    • "Express.js Guide" by Azat Mardan
  4. Tutorials and Articles:

  5. Community and Forums:

Step 8: Build Real-World Projects

  1. Choose Real-World Projects:

    • Build applications like a blog, e-commerce site, or social media app.
  2. Contribute to Open Source:

    • Contribute to open source Express.js projects on GitHub.

Step 9: Stay Updated

  1. Follow Node.js and Express.js Updates:
    • Follow the Node.js blog
    • Join Node.js and Express.js newsletters
    • Attend Node.js and Express.js conferences and meetups

By following this structured guide and practicing regularly, you'll build up your knowledge and skills in Express.js, enabling you to create powerful and efficient server-side applications. If you have any specific questions or need further details on any step, feel free to ask!

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