Learn EXPRESS-JS with Real Code Examples

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

app.use(express.json())

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

let count = 0
app.get('/counter', (req, res) => {
    res.json({ count })
})
app.post('/counter/increment', (req, res) => {
    count++
    res.json({ count })
})
app.post('/counter/decrement', (req, res) => {
    count--
    res.json({ count })
})
app.post('/counter/reset', (req, res) => {
    count = 0
    res.json({ count })
})

app.listen(port, () => {
    console.log(`Server running at http://localhost:${port}`)
})

Demonstrates a simple Express.js REST API with basic routes and middleware.

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

app.get('/greet', (req, res) => {
    const name = req.query.name || 'Guest'
    res.send(`Hello, ${name}!`)
})

app.listen(port, () => {
    console.log(`Server running at http://localhost:${port}`)
})

Handle query parameters in GET requests.

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

app.get('/user/:id', (req, res) => {
    const userId = req.params.id
    res.send(`User ID: ${userId}`)
})

app.listen(port, () => {
    console.log(`Server running at http://localhost:${port}`)
})

Handle dynamic URL parameters in Express routes.

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

app.use(express.json())

app.post('/echo', (req, res) => {
    res.json({ received: req.body })
})

app.listen(port, () => {
    console.log(`Server running at http://localhost:${port}`)
})

Parse JSON body data in POST requests.

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

app.use((req, res, next) => {
    console.log(`${req.method} ${req.url}`)
    next()
})

app.get('/', (req, res) => {
    res.send('Middleware example')
})

app.listen(port, () => {
    console.log(`Server running at http://localhost:${port}`)
})

Demonstrates custom middleware logging requests.

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

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

app.listen(port, () => {
    console.log(`Server running at http://localhost:${port}`)
})

Serve static files using Express.

const express = require('express')
const app = express()
const router = express.Router()
const port = 3000

router.get('/hello', (req, res) => {
    res.send('Hello from router')
})

app.use('/api', router)

app.listen(port, () => {
    console.log(`Server running at http://localhost:${port}`)
})

Organize routes using Express Router.

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

app.get('/error', (req, res) => {
    throw new Error('Something went wrong')
})

app.use((err, req, res, next) => {
    console.error(err.message)
    res.status(500).send('Server Error')
})

app.listen(port, () => {
    console.log(`Server running at http://localhost:${port}`)
})

Custom error handling middleware in Express.

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

app.use(cors())
app.get('/', (req, res) => {
    res.send('CORS enabled')
})

app.listen(port, () => {
    console.log(`Server running at http://localhost:${port}`)
})

Enable CORS for all routes using Express.js.

require('dotenv').config()
const express = require('express')
const app = express()
const port = process.env.PORT || 3000

app.get('/', (req, res) => {
    res.send(`Server running on port ${port}`)
})

app.listen(port, () => {
    console.log(`Server running at http://localhost:${port}`)
})

Access environment variables using Express and Node.js.