Node.js Workshop

© 2015 PayPal Inc. All rights reserved. Confidential and proprietary.

Node.js Workshop

Quhan ArunasalamMarch / 27 / 2015 NTU-IEEE

© 2015 PayPal Inc. All rights reserved. Confidential and proprietary

Node.jsAn open source, cross-platform runtime environment for server-side Javascript applications.

NPM A package manager for Javascript.

Express A minimal and flexible Node.js web application framework.

What we’re going to explore today

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Node.jsRun Javascript on the server

3


Understanding the Event LoopThe guts of Node

4


DoJSON based REST APIs Web / Mobile-Web Apps Network Apps

Don’t CPU intensive work

When to use Node?

5


Test the waters via REPLThe Read-Eval-Print Loop

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• Provides a way to interactively run JavaScript and see the results.

• Useful for debugging, testing, or just trying things out.

https://www.flickr.com/photos/snype451/5752753663/



Lab 2.1: Test the waters via REPLRead-Eval-Print-Loop

7

$ node

> var a = [1, 2, 3];

> console.log(a); [ 1, 2, 3 ]

> a.forEach(function (z) { console.log(z); }); 1 2 3


Lab 2.2: Baby-stepsBuilding the classic Hello World

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$ mkdir hello && cd hello

$ touch index.js

// index.js console.log('Hello NTU');

$ node index Hello NTU

https://www.flickr.com/photos/munakz/9228501911/



The module systemThe building blocks of a Node app

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http://pixabay.com/en/lego-building-blocks-shapes-puzzle-297773/

• Makes it possible to include other Javascript files into your app.

• Helps organize your code into separate parts with limited responsibilities.

• Using modules is simple - You just require() them.



Lab 2.3: Requiring thingsModifying your previous Hello World example

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$ touch greet.js

// greet.js exports.hello = function () { return 'Hello NTU';

}

// index.js var greet = require('./greet.js'); console.log(greet.hello());

$ node index Hello NTU


Lab 2.4: Requiring things (again)Let’s get bilingual

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// greet.js exports.hello = function () { return 'Hello NTU';

} exports.konbanwa = function () { return 'Konbanwa NTU';

}

// index.js var greet = require('./greet.js'); console.log(greet.hello()); console.log(greet.konbanwa());

$ node index Hello NTU Konbanwa NTU


Lab 2.5: Requiring things (one last time)Another way of handling exports

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// greet.js module.exports = {

hello: function () { return 'Hello NTU'; },

konbanwa: function () { return 'Konbanwa NTU'; }

};


In-built modulesDon’t worry, we’re getting to the fun parts

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http://commons.wikimedia.org/wiki/File:AMC_V8_engine_360_CID_customized_um.JPG

Node ships with a number of core modules. For example:

• console - Sends output to

stdout or stderr.

• http - Provides a server and

client for HTTP traffic.

• fs - Provides functions to

interact with the file system.



Lab 2.6: Create a better (Hello) WorldBy building a web server

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// index.js var http = require('http'); var greet = require('./greet.js');

http.createServer(function (req, res) { res.writeHead(200, {'Content-‐Type': 'text/plain'}); res.end(greet.hello()); }).listen(8000);

console.log('Server running at http://127.0.0.1:8000');


Reuse and share code

NPM

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What is npm?It’s 3 things actually

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https://www.flickr.com/photos/kamshots/3096111340/

• A module registry, containing a collection of open-source code.

• A standard, to define dependencies on other packages.

• A package manager, for locally installed modules.



The npmjs.com registryNote the 134,726 packages available (at the time of screenshot)

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Lab 2.7: Initializing your Hello World projectWith metadata

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$ npm init

...

name: (hello) version: (1.0.0) description: An app to say Hello NTU entry point: (index.js) test command: git repository: keywords: helloworld author: Quhan Arunasalam license: (ISC)


Lab 2.8: Saving the momentInstalling and using a 3rd party module

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$ npm install -‐-‐save moment

// index.js var http = require('http'); var greet = require('./greet.js'); var moment = require('moment');

http.createServer(function (req, res) { res.writeHead(200, {'Content-‐Type': 'text/plain'}); res.end('Hi! It is now ' + moment().format('h:mm:ss a')); }).listen(8000);

© 2015 PayPal Inc. All rights reserved. Confidential and proprietary 20

Figuring out package.json

{ "name": "hello", "version": "1.0.0", "description": "An app to say Hello NTU", "main": "index.js", "scripts": { "test": "echo \"Error: no test specified\" && exit 1" }, "keywords": [ "helloworld" ], "author": "Quhan Arunasalam", "license": "ISC", "dependencies": { "moment": "^2.9.0" } }


Let’s not publish another hello world8814 packages available (at the time of screenshot)

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Let’s not publish another hello worldHiding away your little secrets

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{ "name": "hello", "version": "1.0.0",

"private": true, "description": "An app to say Hello NTU", ... }


ExpressWeb app building, made easier

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What is Express?

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• A framework to help build web applications.

• Is to Node what Sinatra / RoR is to Ruby.

• Makes development easier with:

• Request routing

• Handling HTTP verbs

• And a whole lot more...

• Is made up of a series of middleware calls.

http://pixabay.com/en/tunnel-light-speed-fast-auto-101976/

http://pixabay.com/en/tunnel-light-speed-fast-auto-101976/


Lab 2.9: Expressive greetingsModify your Hello World code to use Express

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$ npm install -‐-‐save express

// index.js var express = require('express'); var greet = require('./greet.js'); var app = express();

app.get('/', function (req, res) { res.send(greet.hello());

});

app.listen(8000);


Middleware

Middleware

Middleware

ApplicationRequest Response

A function with access to the request object, the response object, and the next middleware in line in the request-response cycle of an application.


Lab 2.10: Building an API serverTo list and save tasks. And yay! Finally done with the Hello World!

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$ mkdir tasks && cd tasks

$ npm init ...

$ npm install -‐-‐save express $ npm install -‐-‐save express-‐session $ npm install -‐-‐save body-‐parser

$ touch index.js


Lab 2.10: Building an API serverSetting up the Express skeleton

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// index.js var express = require('express'); var session = require('express-‐session'); var bodyParser = require('body-‐parser'); var app = express();

app.listen(3000, function () { console.log('API server started on port 3000'); });


Lab 2.10: Building an API serverSetting up middleware (and some dummy data)

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... var app = express();

app.use(session({secret: 'ntu-‐ieee'})); app.use(bodyParser.urlencoded({extended: false}));

function initializeTasks() { var tasks = []; tasks.push('Step 1: Learn Node'); tasks.push('Step 2: Learn NPM'); tasks.push('Step 3: Learn Express'); return tasks; }

app.listen(3000, function () { ...


Lab 2.10: Building an API serverListing out tasks via GET

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...

app.get('/', function (req, res) { if (!req.session.tasks) {

// Tasks not found in session, so initialize it req.session.tasks = initializeTasks();

}

// Returns a JSON object with an array of tasks res.json({tasks: req.session.tasks}); });

...


Lab 2.10: Building an API serverTesting it out by GETing a list of tasks (via Postman)

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Lab 2.10: Building an API serverAdd a task via POST

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...

app.post('/task', function (req, res) { if (!req.session.tasks) { // Tasks not found in session, so initialize it req.session.tasks = initializeTasks(); }

// Assign the POSTed task to the newTask variable var newTask = req.body.task; // Save the new task to the session array of tasks req.session.tasks.push(newTask); // Returns a JSON object with an array of tasks res.json({tasks: req.session.tasks}); });

...


Lab 2.10: Building an API serverTesting it out by POSTing a new task (via Postman)

33


Cheatsheet

https://github.com/nodeworkshop/node

https://github.com/nodeworkshop/node

© 2015 PayPal Inc. All rights reserved. Confidential and proprietary.

For more information, please contact:

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Quhan Arunasalam

Technology

Node.js Workshop