The document provides an overview of Node.js and the Express web framework. It discusses that Node.js is a platform for executing JavaScript files and includes utilities for network and file I/O. Express is a web application framework built on Node.js that uses middleware to handle requests. The document covers Express concepts like routing, middleware, templating, and popular middleware modules for tasks like compression, parsing request bodies, and sessions.

1. Building Web Apps
using Node.js
@DaveChubbuck
https://github.com/davidchubbs

2. What is Node.js?
# file called: useless.js
console.log(‘Hello world’);
# if useless.js was run in the browser:
# if useless.js was run on Node.js, using Terminal:

3. What is Node.js?
# file called: useless.js
console.log(‘Hello world’);
# if useless.js was run in the browser:
# if useless.js was run on Node.js, using Terminal:

4. What is Node.js?
# file called: useless.js
console.log(‘Hello world’);
# if useless.js was run in the browser:
# if useless.js was run on Node.js, using Terminal:

5. Node.js executes
Javascript files.

6. Node.js is a Platform
(not a framework)

7. Node.js is a Platform
(not a framework)
• Node.js includes some utilities to make it consistent with the
browser, like:
• Timer API: setTimeout
• Console API: console.log

8. Node.js is a Platform
• Node.js also includes utilities for various types of network and
file I/O. These include (among others):
• http, https
• Datagram (UDP)
• NET (TCP)
• fs (File System)
(not a framework)

9. Frameworks are interested in organizing your code
and/or providing sugar for faster development.

10. Frameworks are interested in organizing your code
and/or providing sugar for faster development.
Node.js provides minimal, low-level APIs necessary
to do things like build a web-server, command line
tool, etc. Consequentially, we consider it to be a
platform, not a framework, though there are
frameworks built on top of Node.js
Complete API: http://nodejs.org/api/

11. Node.js Modules

12. Scope, Exporting, &
Importing
Including logic from another file does not affect the global
scope. Each file has its own scope, keeping everything in the
file private unless it is exported.

13. module.exports & exports
use module.exports when exporting 1 value,
exports when exporting 2+ values
# exports-example.js
var private = ‘this is private since it is not exported’;
exports.public = ‘this is public’;
exports.method = function () {
return private;
};
# module-exports-example.js
function Constructor () {}
module.exports = Constructor;

14. caveats
Do not ever reassign exports (that’s what module.exports is for).
exports = {}; // DO NOT DO THIS!
Do not use both exports & module.exports in the same module, else
exports will be ignored.
module.exports = ‘this will work’;
exports.name = ‘this will be ignored’;

15. require
To import/include a module, we use require()

16. require
To import/include a module, we use require()
// .js & .json can be omitted
// filepaths can be relative or absolute (using __dirname)
// module name can be a directory if the directory contains index.js or
// ... if package.json `main` property points to alternative file
// 3rd party modules can be just their name (explained later)
var obj = require(__dirname + ’./exports-example’);
var Constructor = require(‘./module-exports-example’);
var thirdParty = require(‘not-yours’);
obj.public //=> ‘this is public’
typeof obj.method //=> ‘function’
typeof Constructor //=> ‘function’
var instance = new Constructor();

17. Module Caching

18. # index.js
var util = require(‘./util’),
example = require(‘./example’);
console.log(util());
# example.js
var util = require(‘./util’);
util();
# util.js
var counter = 0;
module.exports = function () {
return ++counter;
}
>> node index.js # what will this output?

19. # index.js
var util = require(‘./util’),
example = require(‘./example’);
console.log(util());
# example.js
var util = require(‘./util’);
util();
# util.js
var counter = 0;
module.exports = function () {
return ++counter;
}
>> node index.js
2

20. Modules is one of the best things about Node.js
Node’s implementation of modules is done so well
that Node.js projects tend to be super modular,
promoting low coupling & high cohesion
(it also influenced Browserify, which lets us write front-end
JS files using this same modular pattern)

22. {
"name": "package-name",
"version": "1.0.0",
"description": "",
"author": {
package.json
"name": "David Chubbs",
"url": "https://github.com/davidchubbs"
},
"private": true,
"main": "./server.js",
"scripts": {
"test": "mocha",
"start": "node server.js"
},
"dependencies": {
"express": "^4.0.0"
},
"devDependencies": {
"jshint": "~2.5",
"mocha": "~1.21",
"should": "~4.0"
},
"engines": {
"node": ">=0.10.0"
}
}

23. # install dependencies - will show up in ./node_modules/
npm install # install packages in package.json file
npm install --production # do not install devDependencies
npm install name # install name package
# to save that dependency in your package.json file, use:
npm install name --save-dev # saves to devDependencies
npm install name --save # saves to dependencies
npm rm name # remove package
npm rm name --save # remove from package.json also
npm outdated # check if dependencies are outdated
npm outdated name # check if name is outdated
npm run name # execute scripts.name in package.json
npm start # shortcut for `npm run start`
npm test # shortcut for `npm run test`
npm rm --help # get help on a command
npm install name -g # run command globally

24. express

25. Middleware
Middleware is a design pattern akin to a pipeline. Requests start at
the top and flow until a particular middleware fails to use next()
var express = require('express');
var app = express();
app.use(function (req, res, next) {
res.set('X-Header', 'From Express :)');
next();
});
app.use(function (req, res) {
res.send('this is where you will stop');
});
app.use(function (req, res, next) {
res.send('you will never see this');
});
app.listen(3000);

26. Middleware
Middleware is a design pattern akin to a pipeline. Requests start at
the top and flow until a particular middleware fails to use next()
>> curl -i http://localhost:3000
HTTP/1.1 200 OK
X-Header: From Express :)
Content-Type: text/html;
charset=utf-8
Content-Length: 27
Connection: keep-alive
this is where you will stop
var express = require('express');
var app = express();
app.use(function (req, res, next) {
res.set('X-Header', 'From Express :)');
next();
});
app.use(function (req, res) {
res.send('this is where you will stop');
});
app.use(function (req, res, next) {
res.send('you will never see this');
});
app.listen(3000);

27. Mounting
Middleware can be mounted to base directories.
...
app.use('/users', function (req, res, next) {
res.set('X-Role', 'User');
next();
});
app.use('/admins', function (req, res, next) {
res.set('X-Role', 'Admin');
next();
});
app.use(function (req, res, next) {
res.send('this is where you will stop');
});
...

28. Mounting
Middleware can be mounted to base directories.
...
app.use('/users', function (req, res, next) {
res.set('X-Role', 'User');
next();
});
app.use('/admins', function (req, res, next) {
res.set('X-Role', 'Admin');
next();
});
app.use(function (req, res, next) {
res.send('this is where you will stop');
});
...
>> curl -i http://localhost:
3000/admins/index
HTTP/1.1 200 OK
X-Role: Admin
Content-Type: text/html;
charset=utf-8
Content-Length: 27
Connection: keep-alive
this is where you will stop

29. Mounting
Middleware can be mounted to base directories.
...
app.use('/users', function (req, res, next) {
res.set('X-Role', 'User');
next();
});
app.use('/admins', function (req, res, next) {
res.set('X-Role', 'Admin');
next();
});
app.use(function (req, res, next) {
res.send('this is where you will stop');
});
...
>> curl -i http://localhost:
3000/admins/index
HTTP/1.1 200 OK
X-Role: Admin
Content-Type: text/html;
charset=utf-8
Content-Length: 27
Connection: keep-alive
this is where you will stop
>> curl -i http://localhost:
3000/users
HTTP/1.1 200 OK
X-Role: User
Content-Type: text/html;
charset=utf-8
Content-Length: 27
Connection: keep-alive
this is where you will stop

30. Mounting
The base directory is stripped from the mounted middleware function, meaning
the mounted middleware does not have to understand where it is mounted.
...
app.use('/admins', function (req, res) {
res.send(req.url);
});
...

31. Mounting
The base directory is stripped from the mounted middleware function, meaning
the mounted middleware does not have to understand where it is mounted.
...
app.use('/admins', function (req, res) {
res.send(req.url);
});
...
>> curl -i http://localhost:
3000/admins/index
HTTP/1.1 200 OK
Content-Type: text/html;
charset=utf-8
Content-Length: 27
Connection: keep-alive
/index

32. Routing

33. app.get('/profile', function (req, res) {
res.send('view profiles');
});
app.post('/profile', function (req, res) {
res.send('update profiles');
});

34. app.get('/profile', function (req, res) {
res.send('view profiles');
});
app.post('/profile', function (req, res) {
res.send('update profiles');
});
app.get('/profile/:id', function (req, res) {
res.send('profile w/ id: ' + req.params.id);
});

35. app.get('/profile', function (req, res) {
res.send('view profiles');
});
app.post('/profile', function (req, res) {
res.send('update profiles');
});
app.get('/profile/:id', function (req, res) {
res.send('profile w/ id: ' + req.params.id);
});
app.param('name', function (req, res, next, name) {
// load user before hand using `name` - add to req.user
next();
});
app.get('/user/:name', function (req, res) {
// use req.user
});

36. app.all(‘/any-http-method’, function (req, res) {
// no matter the http-method (GET, POST, PUT, etc.)
// this will catch all requests @ /any-http-method
...
});
app.route(‘/write/path/once’)
.all(function (req, res, next) {
// do something BEFORE method-specific handling
next();
.get(function (req, res) {
...
})
.post(function (req, res) {
...
});

37. // Routers are isolated, making them akin to mini-apps
var router = express.Router(); // create a router
// add custom middleware to router
router.use(function (req, res, next) {
next(); // use like any other middleware
});
// add routes
router.route(‘/profile’)
.get(function (req, res) {
...
});
app.use(‘/users’, router);

38. // catching 404’s involves having a route like this after your routes
app.use(function (req, res) {
res.status(404).send(‘Page not found’);
});
// then catch 500’s
// (all 4 arguments are required)
app.use(function (err, req, res, next) {
console.error(err);
res.status(500).send(‘Server error occurred’);
});

39. // if an error occurs, you can immediately pass control to
// your 500/error route by returning next(err)
app.param(‘id’, function (req, res, next, id) {
User.find(id, function (err, user) {
if (err) {
return next(new Error(‘User could not be found’));
}
req.user = user;
next();
});
});

40. Popular Middleware
& Configuration

41. // setup templating
// ================
var cons = require(‘consolidate’);
// set .ejs files will use EJS templating engine
app.engine(‘ejs’, cons.ejs);
// set .ejs as the default extension
app.set(‘view engine’, ‘ejs’);
// set templates path
app.set(‘views’, __dirname + ‘/views’);
// render template
// ===============
app.get(‘/path’, function (req, res) {
// renders template: __dirname + ’/views/template-file.ejs’
res.render(‘template-file’, { dynamicData: 1 });
});

42. var compress = require('compression');
var bodyParser = require('body-parser');
var logger = require('morgan');
app.use(compress());
app.use(bodyParser());
app.use(express.static(__dirname + '/public'));
app.use(logger('dev'));
// or write custom syntax - :method :url :status :res[content-length]

43. var cookie = require('cookie-parser');
var session = require('express-session');
var RedisSession = require("connect-redis")(session);
// option 1: basic cookies
app.use(cookie());
// in middleware, use res.cookie('name', 'value') to set,
req.cookies.name to get
// option 2: signed cookies
app.use(cookie("secret-used-to-sign-cookies"));
// res.cookie('name', 'value', {signed: true}), req.signedCookies.name
// option 3: sessions
app.use(cookie());
app.use(session({
store : new RedisSession({ port:6379, host:'localhost' }),
name : 'sessions',
secret: 'secrect-session-hash',
cookie: { maxAge : 10800 * 1000 } // seconds * milliseconds
}));
// option 4: see example using passport for auth

44. req & res

45. req.params //=> {object} route paramaters
req.query //=> {object} parsed query-string ?n=value => {n:value}
req.body //=> {object} parsed form input
req.route //=> {object} matched route details
req.get(header) //=> {string} get header field (case insensitive)
req.ip
req.path
req.url //=> {string} .path + .query
req.baseUrl //=> {string} prefix when mounted
req.originalUrl //=> {string} .baseUrl + .url (untouched)
req.secure //=> {boolean} if SSL is used
req.hostname //=> {string} header Host value
req.subdomains //=> {array}

46. res.set(headerName, value)
res.status(404) // set status code of response
res.cookie(name, value, [options])
res.clearCookie(name, [options])
// generating a response packet
// ============================
res.send(data)
res.render(template, [data, callback])
res.json(data)
res.redirect([status=302], url)
// url can be host relative (‘/path’) or path relative (‘add-to-path’)

47. Go to http://expressjs.com/4x/api.html
for the full API docs.
This will flesh out the remaining
`req` & `res` object properties.