Node.js framework express.js middleware All In One

Node.js framework express.js middleware All In One

express.js middlewares order

writing middleware

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

const myLogger = function (req, res, next) {
  console.log('LOGGED')
  next()
}

app.use(myLogger)

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

app.listen(3000)

https://expressjs.com/en/guide/writing-middleware.html

demos

// const express = require('express')
import express from 'express';
const app = express()

const middleware1 = function (req, res, next) {
  console.log(`middleware 1 ✅`)
  next()
}

const middleware2 = (req, res, next) => {
  console.log(`middleware 2 ✅✅`)
  next()
}

const middleware3 = (req, res, next) => {
  console.log(`middleware 3 ✅✅✅`)
  next()
}

app.use(middleware1)
app.use(middleware2)
app.use(middleware3)

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

// app.listen(3000)
const PORT = 3000;
app.listen(PORT, () => {
  console.log(`server is running on http://localhost:${PORT}`);
})

http://localhost:3000/

// const express = require('express')
import express from 'express';
const app = express()

const middleware1 = function (req, res, next) {
  console.log(`middleware 1 ✅`)
  next()
}

const middleware2 = (req, res, next) => {
  console.log(`middleware 2 ✅✅`)
  next()
}

const middleware3 = (req, res, next) => {
  console.log(`middleware 3 ✅✅✅`)
  next()
}

app.use(middleware1, middleware2, middleware3);

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

// app.listen(3000)
const PORT = 3000;
app.listen(PORT, () => {
  console.log(`server is running on http://localhost:${PORT}`);
})

// const express = require('express')
// const bodyParser = require('body-parser');
import express from 'express';
import bodyParser from 'body-parser';
import router from './routers/index.js';

const app = express()

// ❌
app.use(router)

// get POST request's body
app.use(bodyParser.json())
app.use(bodyParser.urlencoded({extended: true}))

// // ✅
// app.use(router)
const auth = (req, res, next) => {
  console.log(`req.originalUrl`, req.originalUrl);
  if(req.originalUrl) {
    next()
    // ⚠️
    return;
  }
  res.send(`403 error`);
}

const middleware1 = function (req, res, next) {
  console.log(`middleware 1 ✅ before`)
  next()
  console.log(`middleware 1 ✅ after`)
}

const middleware2 = (req, res, next) => {
  console.log(`middleware 2 ✅✅ before`)
  next()
  console.log(`middleware 2 ✅✅ after`)
}

const middleware3 = (req, res, next) => {
  console.log(`middleware 3 ✅✅✅ before`)
  next()
  console.log(`middleware 3 ✅✅✅ after`)
}

app.use(middleware1, middleware2, middleware3);

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

// app.listen(3000)
const PORT = 3000;
app.listen(PORT, () => {
  console.log(`server is running on http://localhost:${PORT}`);
})
// http://localhost:3000

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video tutorials

refs

https://stackoverflow.com/questions/77452391/req-body-is-undefined-when-use-router-post-but-visible-when-use-app-post

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