Introduction to Node.js

ramit@ischool.berkeley.edu

School of Information, UC Berkeley

What is Node.js?

"Node.js is a platform built on Chrome’s JavaScript runtime for easily building fast, scalable network applications. Node.js uses an event-driven, non-blocking I/O model that makes it lightweight and efficient, perfect for data-intensive real-time applications that run across distributed devices."

.... What does this mean?
A platform that makes writing powerful C/C++ server-side apps easy by essentially wrapping them in JavaScript.

Node.js is the world's answer to having a single unified language across tiers!
Server Side Javascript!!
Almost every page served to you uses javascript on the web.
JS is not going anywhere, so why not make JS pervasive across tiers?
Why? Well to eliminate the need for different programmers for front end and backend programming
Need more reasons? JS is super fast! ...
... AND allows for extremely rapid development of web applications
Built on Chrome V8 Engine - Google’s open source, C++ based JavaScript engine that actually runs JavaScript. The Node.js team took this C++ code and added other important libraries like TCP, HTTP and DNS to create Node.js.

But why Node.js?

Multiple threads are great for fast and scalable server side applications. But those are difficult to make and maintain!...
Multi-threaded servers supporting a synchronous, blocking I/O model provide a simpler way of performing I/O. More threads = more memory and higher CPU usage for context switching

Enter Node.js

Node.js performs Event-driven, non-blocking I/O
So, Node uses an event loop (main and only thread) at the front and performs asynchronous I/O at the kernel level. Fewer Threads = Less context switching = less memory and cpu usage

Benefits

Savings in I/O cost (i.e., high performance)
Savings in Memory
JavaScript
Thousands of libraries!

When to use Node.js?

Build a (soft) real-time social app like Twitter or a chat app.
Build high-performance, high I/O, TCP apps like proxy servers, PaaS, databases, etc.
Add a RESTful API-based web server in front of an application server.

When NOT to use Node.js?

Mission-critical (hard) real-time apps like heart monitoring apps or those that are CPU-intensive.
For simple CRUD apps that don’t have any real-time or high-performance needs, Node.js does not provide much of an advantage over other languages.

Demos!

Install node.js!

var http = require("http");
http.createServer(function(request, response) {
  response.writeHead(200, {"Content-Type": "text/plain"});
  response.write("Hello World");
  response.end();
}).listen(8888);

Modules and basic routing demo