lesson4.md

Lesson 4 - Intro to Express JS

You can serve HTML and JS files with ExpressJS. You can also build dynamic web sites with Express JS as well.

Exercise 4.1

Scenario: Serve a basic NodeJS app

Objective:

• Create a web server using Express JS
• Server simple dynamic sites using NodeJS

Steps:

1. In your Terminal / Command Prompt, create a new folder called myapp

   mkdir myapp
   cd myapp

2. Create a new NPM package

   npm init

   Use the default for everything excpet the Entry Point. Change it to app.js.

3. Add Express JS package

   npm install express --save

4. Open the myapp folder in Visual Studio Code.

5. Create a new file called app.js

   Copy and paste the contents below into app.js.

   const express = require('express')
   const app = express()
   const port = 3000
   
   app.get('/', (req, res) => {
     const name = req.query.name || 'World'
     res.send('Hello ' + name + '!')
   })
   
   app.listen(port, () => console.log(`Example app listening on port ${port}!`))

   Remember to save the file!

6. Start the ExpressJS server

   node app.js

7. Open your browser and go to: http://localhost:3000

8. Try changing the name: http://localhost:3000?name=Elisha

Further Reading

• https://expressjs.com/en/starter/installing.html

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Exercise 4.2

Scenario: Here's an easier way to bootstrap an ExpressJS app

Objective:

• Create a web server using Express's Generator

Steps:

1. Using Terminal or Command Prompt, create a new folder: myapp2

   mkdir myapp2
   cd myapp2

2. Type this commands:

   npx express-generator
   npm install

3. You can start the app like this:

   DEBUG=myapp2:* npm start

4. Visit the site in your browser: http://localhost:3000

Further Reading

• https://expressjs.com/en/starter/generator.html

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Next: Lesson 5 - Build a simple web app ≫