Introduction to Developing applications using node.js on Bluemix

1. Introduction to Developing applications using node.js on Bluemix IBM Ecosystem Development Instructors : • Krishnaprasad Subbarao, • Abhay Ratnaparkhi

2. Agenda • Introduction to node.js • What is node.js • node.js first app • Components of node.js • node.js api • node.js modules • Express • npm • Developing a node.js application on Bluemix • IBM DevOps Services for Bluemix • Developing IOT application on Bluemix

3. What is node.js • open source, cross-platform runtime environment for server-side and networking applications • Server side Java script system • applications are written in JavaScript, and can be run within the Node.js runtime. • contains a built-in library to allow applications to act as a Web server • Powered by Google 8 runtime • provides an event-driven architecture and a non-blocking I/O API • commonly used for real-time web applications.

4. node.js first app • Download link : http://nodejs.org/download/ • First program HelloWord.js var http = require('http'); http.createServer(function (req, res) { res.writeHead(200, {'Content-Type': 'text/plain'}); res.end('Hello World\n'); }).listen(1337, "127.0.0.1"); console.log('Server running at http://127.0.0.1:1337/'); • Cmd> node HelloWorld.js Server running at http://127.0.0.1:1337/ • http://localhost:1337/

5. node.js : Components

6. node.js Components continued.. • Application : the user developed application • Java script : prototype based scripting language • V8 Javascript Engine : • Open source javascript engine developed by Google • Used by Chrome, Node.js • Bindings : programs that make V8 and the library able to talk to each other. • e.g. binding for database libraries • https://pravinchavan.wordpress.com/2013/11/08/c-binding-with-node-js/

7. node.js Components continued.. • LIBUV : • a multi-platform support library • focuss on asynchronous I/O • primarily developed for use by Node.js • also used by Luvit, Julia, pyuv and few others • Event loop • Non thread safe • Handles – long lived objects e.g. a TCP server handle • Call backs are called when an event occurs • Requests • Short lived operations run directly on the loop

8. node.js api • Provides large number of built in functions, modules, add ons • http://nodejs.org/api/index.html • HTTP • provides a way to develop an http server which can process http requests • Globals • require : A reference to a function used to require modules. • module : A reference to the current module • exports :A reference to the module.exports variable • console : For printing to stdout and stderr.

9. node.js modules • A Node/npm module is just an simple JavaScript file • follows the CommonJS module spec. • encapsulates related code into a single unit of code • Allows building re-usable code • Samples modules : http, express

10. node.js modules continued.. • // greetings.js sayHelloInEnglish = function() { return "Hello"; }; sayHelloInSpanish = function() { return "Hola"; };

11. node.js modules continued.. • // greetings.js // var exports = module.exports = {}; exports.sayHelloInEnglish = function() { return "HELLO"; }; exports.sayHelloInSpanish = function() { return "Hola"; };

12. node.js modules continued.. • // main.js var greetings = require("./greetings.js"); • Equivalent to var greetings = { sayHelloInEnglish: function() { return "HELLO"; }, sayHelloInSpanish: function() { return "Hola"; } };

13. Express • Express : • minimal and flexible Node.js web application framework • provides a robust set of features for web and mobile applications. • http://expressjs.com/ • Provides 4 objects • Application - app • holds the settings of the express application • HTTP request – req • provides a way to read all the request parameters, query string, request body for POST requests

14. Express continued.. • Express : • Objects • HTTP response - res • provides ways to return the response back to the client. • Router – Router • accepts a set of functions attached to a path • executed when a request for the attached path or any inner path is received

15. Express continued.. • HelloWorldExpress.js var express = require('express') var app = express() app.get('/', function (req, res) { res.send('Hello World!') }) var server = app.listen(3000, function () { var host = server.address().address var port = server.address().port console.log('Example app listening at http://%s:%s', host, port) })

16. npm • pre-installed package manager for the Node.js server platform. • It is used to install Node.js programs from the npm registry • npm init - creates a new package • npm install • e.g. npm install express –save • Install express and adds to package.json

17. Package.json • Contains complete structure of the application. • all packaging, dependency and version related information. • important contents • main : module ID that is the primary entry point to your program • License : license information of the module. • man : to specify the help contents about this package • config : to set configuration parameters used in package scripts • Dependencies : list modules on which this module is dependent

18. Package.json { "name": "samples", "version": "1.0.0", "description": "Node.js introduction samples", "main": "HelloWorld-express.js", "scripts": { "test": "echo \"Error: no test specified\" && exit 1" }, "license": "ibm", "dependencies": { "express": "^4.11.0" } }

19. Developing a node.js application on Bluemix