This document provides an introduction to Express, a web application framework for Node.js. It demonstrates how to quickly generate an Express app, explain its default structure and files, and shows examples of serving static files, using views, and defining routes and APIs to handle requests. Key aspects covered include using middleware like the body parser and static file serving, as well as rendering views and sending JSON responses.

1. Intro to Express
Web Application Framework for Node
Created by /Jason Sich @jasich

2. Let's make a Web App!
//Installtheexpressgenerator
$npminstall-gexpress-generator
//Createanewexpressapp
$expresshelloGrNodeDev
$cd./helloGrNodeDev
//Installdependenciesforexpress
$npminstall
//Runit!
$npmstart
...
Expressserverlisteningonport3000

3. Well that was almost too easy
While running the express generator I had 2 issues that I had to fix
before being able to load the main page.

4. Sidenote: Modules
There are a ton of modules out there, but not all of them get updated in
a timely manner.
When dependencies break your app it can be painful to fix.

5. Default Structure
app.js =>Expressserver
package.json =>NPMpacakgefile
public =>Staticdirectorytoserveupfilesfrom
-images
-javascripts
-stylesheets
routes =>Defineyourroutinghere
views =>Containshtmlviews
This structure can be modified to suit your needs. Express does not
force any conventions on you.

6. Simple Server
varexpress=require('express');
varapp=express();
app.get('/hello',function(req,res){
res.send('HelloWorld');
});
varserver=app.listen(3000,function(){
console.log('Listeningonport%d',server.address().port);
});

7. Serving Files Statically
varpath=require('path');
//Servestaticfilesdirectlyfromthe'public'directory
app.use(express.static(path.join(__dirname,'public')));

8. Using Dynamic Views
//Setsthelocationofourtemplatefilesforviews
//Thisiswhereallthejadetemplatesgo
app.set('views',path.join(__dirname,'views'));
//Setstheviewengineto'jade'becausewe'resoEmo
app.set('viewengine','jade');
//ForHTTPGETrequestsserveuptheindexview
//Setthetitleto'Express'
app.get('/',function(req,res){
res.render('index',{title:'Express'});
});

9. All Together Now
varexpress=require('express'),
path=require('path');
varapp=express();
app.set('views',path.join(__dirname,'views'));
app.set('viewengine','jade');
app.use(express.static(path.join(__dirname,'public')));
app.get('/',function(req,res){
res.render('index',{title:'Express'});
});
app.listen(3000,function(){
console.log('Listeningonport%d',server.address().port);
});

10. Example Jade Template
//index.jade
doctypehtml
html
head
title=title
link(rel='stylesheet',href='/stylesheets/style.css')
body
h1=title
pWelcometo#{title}

11. It Needs an API
Let's say we are using a front-end JS framework and need to serve up
some data in JSON.

12. Shut the Front Door, That Easy?
//RegistersahandlerforanHTTPGETrequestto'/animals'
app.get('/animals',function(req,res){
varanimals=[
{name:'SharkOwl'},
{name:'Liger'},
{name:'Zebroid'}
];
//Justsendthearrayasaresponse
res.send(animals);
});

13. And a Post?
.
app.use(express.bodyParser());
.
//RegistersahandlerforanHTTPPOSTrequestto'/animals'
app.post('/animals',function(req,res){
varnewAnimal=req.body;
//Lettheclientknowthatthingsarecoolwithus
res.send(201,{success:true});
});

14. What's up with app.use()?
It registers middleware in your Express application. Middleware is
additional functionality injected into request handling.
There is an order to middleware. If one piece of middleware services a
request, the request is considered handled and the rest of the
middleware is not used.

15. For example we can register the 'express.static' middleware to serve up
static files for requests.
app.use(express.static(path.join(__dirname,'public')));

16. Or we can define our own:
app.use(function(req,res,next){
if(!req.get('authorization')){
res.Send(403,"NotAllowedSon,BetterLuckNextTime");
}else{
next();
}
});

17. The End
BY Jason Sich