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ImprovingU

Node Revolution

Kris McGinnes

Agenda

  • What is Node
  • When is Node
  • Why to Node
  • How to Node

What is Node.js

What is Node.js

  • Google's V8 JavaScript engine
  • Event driven
  • Non-blocking standard libraries
  • Most APIs speak Streams
  • Extensible via C/C++ add-ons
  • Provides a package manager and module system for JS/native extensions
  • EcmaScript 5 (Node v0.12.) & EcmaScript 6 (Node 4.)
  • JIT & optimized JavaScript

What is Node.js

Node.js® is a JavaScript runtime built on Chrome's V8 JavaScript engine. Node.js uses an event-driven, non-blocking I/O model that makes it lightweight and efficient. Node.js' package ecosystem, npm, is the largest ecosystem of open source libraries in the world.

What is Node.js

It's important to remember that Node is really two things: a runtime environment and a set of libraries. Like .Net is the CLR and the base class libraries. The Node libraries have first class support for things like HTTP requests and non-blocking IO calls.

Mapping the nomenclature

I stole this slide from Shawn Wildermouth's great Node.js course on PluralSight. I highly recomend checking it out. It influenced a lot of what you are learning here.

IIS => Node.exe C#/VB => JavaScript EF/SQL Server => MongoDB or other database ASP.Net Web Forms => Express + EJS ASP.Net MVC/Razor => Express + Jade/Razor ASP.Net Web API => Express Angular/Ember/KnockoutJS => Angular/Ember/KnockoutJS SignalR => WebSockets/Socket.io

Dependency managment

  • Like RequireJS but different
  • The require keyword takes a path to a file
  • Uses exports as the returned object
  • Executes module code once and caches
  • When assigning a function to exports you must use module.exports

What Node.js is not

  • A framework like Asp.net MVC/Web Forms
  • A new programming language

History

  • 1996 JavaScript released by Netscape
  • 1999 Ajax introduced in Internet Explorer 5
  • 2006 jQuery is released
  • 2008 Google releases V8 JavaScript engine
  • 2009 Ryan Dahl starts Node.js
  • 2011 NPM introduced
  • 2014 Node.js forked and IO.js created
  • 2015 EcmaScript 6 finalized
  • 2015 IO.js merges back into Node.js

Why Node.js

JavaScript everywhere

  • Code reuse
  • Same programming culture on client and server
  • Lots of JavaScript programmers

Vibrant community

  • 190,000+ packages on npm
  • Top corporate sponsers
  • Huge wealth of JavaScript code

Sweet spots

  • Real-time/high concurrency apps (I/O bound)
  • API tier for single page apps and rich clients (iOS/Android)
  • Service orchestration
  • Working with document (JSON-style) databases

Not so sweet spots

  • Simple CRUD apps (lack of frameworks)
  • Not as fast as some for CPU-intensive stuff

How to Node

Standard libraries

  • Async by default
  • Low level
  • HTTP is first class citizen

Demo

var http = require('http');

var server = http.createServer(function(request, response) {
    response.writeHead(200, {
        'Content-Type': 'text/plain'
    });
    response.end('Hello world');
});

server.listen(3000);

console.log("Server listening on http://localhost:3000");

Open http://localhost:3000

Developing and Debugging

  • Lots of different choices
  • nodemon for save, refresh browser workflow
  • node-inspector allows debugging in Chrome
  • IDEs (WebStorm, Eclipse, Visual Studio [Code], etc)

Demo

> npm install -g node-inspector

> node-debug app.js

Open in Chrome http://localhost

CommonJS modules

  • Prevents pollution of the global scope
  • Two style of module development

Demo

Create a simple logger module and import it into our app.

logger.js

exports.info = function(msg) {
    console.log(new Date() + ': ' + msg);
};

exports.error = function(msg) {
    console.error(new Date() + ': ' + msg);
};

Then modify app.js:

var logger = require('./logger');

logger.info('Logging hello world');

Demo

When you want to export a instance factory you must use module.exports.

point.js

function Point(x, y) {
    this.x = x;
    this.y = y;
}

Point.prototype.print = function() {
    console.log(this.x + ', ' + this.y);
}

module.exports = Point;

app.js

var Point = require('./Point');

var point = new Point(25, 36);

point.print();

Async callbacks and error handling

  • Any async function allows you to pass a callback
  • Callback parameters include an Error parameter
  • Errors will bring down the process if not handled

Demo

app.js

var fs = require('fs');

fs.readFile('/', function (err) {
    if(err) throw err;

    console.log('completed');
});

What is NPM

NPM is a command line utility that allows the installation and management of Node modules. These modules can be installed from many sources, but the most common one is npmjs.com.

NPM can install modules into your application, or globally into the system itself.

Every Node application is a module by default.

What is NPM

  • Node standard libraries are
  • require('http') looks on the global Node module path
  • NPM installs packags to a local node_modules folder and adds that to the Node module path
  • require('express') will be found in the local node_modules folder