What is Nodejs

Allows you to build scalable network applications using JavaScript on the server-side.

Nodejs runs on V8 javascript runtime.

Why use NodeJS?

• Simple
• Allows for more control
• Fast (specially with IO and data driven applications)
• Non-Blocking (Asynchronous)

What could you build with Nodejs

• Websocket Server (chat server)
• Web services
• Any Real-Time Data Apps

Let's create a Server

Let's take a look at how we create a server with nodejs, it's very simple.

var http = require('http');

server = http.createServer();

Listen Server!

The server should "listen" on a specific port for a connection.

var http = require('http');

server = http.createServer();

server.listen(1337);
console.log("Server is listening on 1337");

Now we have a running server

Detect a connection event

Nodejs is built around events.

Let's listen to the connection event on the server

var http = require('http');

server = http.createServer();

server.on('connection',function(req,res){
    res.end("hello world");
});

server.listen(1337, '127.0.0.1');

Nodejs is Non-Blocking

What are the things that block?

• Reads/Writes on the Database

• Calls to other web services

• In other web frameworks, we create a separate thread for each request.

• Nodejs uses only one thread!

Events

An event can be, for example:

• Incoming Connection from the client
• Incoming Data from the client
• Server close event.
• event event event.

Events (Continue)

Let's look at our server, what are the events our server can have?

• request
• connection
• close

https://nodejs.org/api/http.html#http_event_request

Block Node

The only way you can block your application is that you don't end the event callback.

var http = require('http');

server = http.createServer();

server.on('connection',function(req,res){

    res.writeHead("hello");
    res.write("hi there");
    console.log("If you don't call res.end node will stop the whole application");
    console.log("This is a very common mistake");

});

server.listen(1337, '127.0.0.1');

Module

Organize our code into files that can be included into each other We use "require" to load our module we have seen it in:

var http = require('http');

Our first module

Let's create a module that:

• take the request object
• get the headers
• return the connection header

Module exports

var requestConnection = function(request){

    console.log(request.headers.connection);

}
module.exports = requestFormatter;

NPM

• Package manager for Node
• Similar to gems in ruby
• Installed locally or globally

Installing packages

use npm install "package_name"