1. Day 1 - The Beginning
2. Day 2 - File System in node.js
3. Day 3 - Regular expressions in node.js
4. Day 4 - Console module in node.js
5. Day 5 - All about errors
6. Day 6 - Array methods
7. Day 7 - All about NPM
8. Day 8 - Publishing package on NPM
9. Day 9 - Crypto Module ( Hashing and HMAC)
10. Day 10 - Crypto Module ( Encryption and Decryption )
11. Day 11 - Express Framework
12. Day 12 - CRUD in MongoDB using node.js
13. Day 13 - Sign Up form in node.js
14. Day 14 - Introduction to socket.io
15. Day 15 - All about streams
16. Day 16 - Zlib Module
17. Day 17 - CRUD in MySQL using node.js
18. Day 18 - Concepts of callbacks in node.js
19. Day 19 - Query String in node.js
20. Day 20 - Timers in node.js
21. Day 21 - Buffers in node.js
22. Day 22 - String Decoder Module in node.js
23. Day 23 - Debugger module in node.js
24. Day 24 - Child Processes in node.js
25. Day 25 - Clusters in node.js
26. Day 26 - OS module in node.js
27. Day 27 - Assert module in node.js
28. Day 28 - Getting Tweets using node.js
29. Day 29 - Uploading file to dropbox using node.js
30. Day 30 - Github API with node.js

Express.js or simply express is a minimal node.js web apps framework which is flexible and provides a set of features such as simple APIs used for building backend of websites and mobile applications. Express is open-source and currently maintained by node.js foundation. Express also provides us with very basic middleware and declarative routing.
Advantages of using express web application framework includes :

1. It makes routing pretty easy.
2. As it is built on top of node.js, so fast I/O.

Prerequisites for installing express are :

1. Node.js - we can check it using the following command on terminal :
   

   											
   >node -v
   v8.5.0
   											
   										

   
   
2. NPM - we can check it using the following command on terminal :
   

   											
   >npm -v
   5.4.2
   											
   										

   
   

We can install express in the following ways :

1. Installing express globally : We can install express with global scope in the following way
   

   											
   >npm install express -g
   											
   										

   
   
2. Installing express locally : We can install express with local scope in the following way
   

   											
   >npm install express 
   											
   										

   
   
3. Installing express with --save flag : We can install express with --save flag to add dependency in the package.json file.
   

   											
   >npm install express --save
   
   											
   										

   
   

Let's create a simple server in express which will send hello world as the response to the user.

											
var express = require('express')
var app = express()

app.get('/', function (req, res) {
  res.send('Hello World!')
})
app.listen(3000, function () {
  console.log('Server is listening at 3000')
})
											
										

											
>node server.js
Server is listening at 3000
											
										

One of the biggest advantage of using express is that it makes routing very simple. An example which explains routes in a very simple way is given below :

											
var express = require('express')
var app = express()

app.get('/', function (req, res) {
  res.send('Simple Example of routes!');
})

app.get('/signup', function (req, res) {
  res.send('This is demo route for sign up');
})

app.get('/signin', function (req, res) {
  res.send('This is demo route for sign in');
})

app.get('/signin/dashboard', function (req, res) {
  res.send('This is demo route for user who signed in and now reaches their dashboard');
})


app.listen(3000, function () {
  console.log('Server is listening at 3000')
})
											
										

											
>node routes.js
Server is listening at 3000
											
										

We can open any of the following in our browser :
• Now open http://127.0.0.1:3000 in your browser for default route
• http://127.0.0.1:3000/signup for demo signup route.
• http://127.0.0.1:3000/signin for demo signin route
• http://127.0.0.1:3000/signin/dashboard for demo dashboard route.

In order to understand how the request with parameters is handled in express let's take an example : Suppose we have a sign up module in which we are receiving 3 parameters from the front-end which are name, email and password. ( Normally, we store data in a database . we will perform that in the coming chapter. For now , just focus on understanding just the request with parameters part)

											
var express = require('express');
var fs = require('fs')

var app = express()

app.get('/', function (req, res) {
  res.send('Simple Example of routes!');
}) 

app.get('/signup', function(req,res){
	// this is how we will receive params from front end 
	
	var name = req.query.name; 
  var email = req.query.email;
  var password = req.query.password;
  //For demo purpose
  console.log(name + '' + email + ' ' + password);

  /**
   * Store this in a database and perform further processing
   */
    res.send("In signup module")
});

app.listen(3000, function () {
  console.log('Server is listening at 3000')
})
											
										

											
>node routes-with-params.js
Server is listening at 3000
											
										

In this chapter of 30 days of node tutorial series, we learned about what is express.js, how to install express , simple server to serve hello world using express , basic about routing and how to handle request params.