Express.js

GuideBookonWebframeworkforNode.js

ByRickL.

Copyright©2016RickL.AllRightsReserved

Copyright©2016byRickL.

All rights reserved. No part of this publication may be reproduced, distributed, ortransmitted in any form or by any means, including photocopying, recording, or otherelectronic or mechanical methods, without the prior written permission of the author,except in the case of brief quotations embodied in critical reviews and certain othernoncommercialusespermittedbycopyrightlaw.

TableofContentsIntroduction

Chapter1-OverviewofExpressJS

Chapter2-Session

Chapter3-serve-index

Chapter4-cookie-Sessions

Chapter5-MorganinExpressJS

Chapter6-CORS

Chapter7-Express-Paginate

Chapter8-Multer

Chapter9-Compression

Chapter10-csurf

Chapter11-body-parser

Chapter12-Flash

method-override

Chapter13-serve-favicon

Chapter14-response-time

Chapter15-express-namespace

Chapter16-express-expose

Chapter17-connect-render

Conclusion

Disclaimer

Whileallattemptshavebeenmadetoverifytheinformationprovidedinthisbook,the author does assume any responsibility for errors, omissions, or contraryinterpretations of the subjectmatter containedwithin. The information provided inthisbookisforeducationalandentertainmentpurposesonly.Thereaderisresponsibleforhisorherownactionsandtheauthordoesnotacceptanyresponsibilitiesforanyliabilitiesordamages,realorperceived,resultingfromtheuseofthisinformation.

The trademarks that are used arewithout any consent, and thepublication of thetrademark is without permission or backing by the trademark owner. Alltrademarksandbrandswithinthisbookareforclarifyingpurposesonlyandaretheownedbytheownersthemselves,notaffiliatedwiththisdocument.

Introduction

ExpressJSisoneofthemostusefulandinterestingNodeframeworks.Itisusedforthe

developmentofbothwebandmobileapplications.Thesetypesofapplicationsarethe

mostlywidelyusedinsoftwareenvironments.Thisshowstheneedforyoutoknowhow

thisframeworkcanbeusedfordevelopment.Theframeworkhasnumerousmodules

whichcanbeusedforthepurposeofenhancingthelookandfeelofyourapplications.

Chapter1-OverviewofExpressJS

ExpressJSisaNodeframeworkwhichisveryflexibleandprovidesdeveloperswith

numerousfeaturesforthedevelopmentofwebandmobileapplications.Theframework

canbeusedforthedevelopmentofAPIs.Inthisbook,wewilldiscussthevariousfeatures

ofExpressJS.

Chapter2-Session

ToinstallthisinExpress,justexecutethefollowingcommand:

$npminstallexpress-session

Theabovecommandwillinstallthesessionintoyoursystem.Touseitinyourprogram,

youhavetousethe“require”command.Thisisshownbelow:

varsession=require(‘express-session’)

Thesessionmiddlewarecanbecreatedbyuseofthegiven“options.”Youshouldknow

thatthedataforthesessionshouldnotbesavedinthecookieitself,buthere,onlythe

sessionIDisstored.Thedataforthesessionisstoredontheserversidefortheapp.

However,“MemoryStore,”whichisthedefaultserver-sidesessionstoragewasnot

developedforuseinaproductionenvironment.Inmostcases,itwillleakandnotscale

pastasingleprocess.Itwasdevelopedforthepurposeofdebugging.

“express-session”willacceptthefollowingpropertiesintheobjectforoptions:

Cookie

ThesearethesettingsforthecookieofthesessionID.Considertheexamplegivenbelow:

{path:‘/’,httpOnly:true,secure:false,maxAge:null}.

Genid

ThisisafunctionwhichiscalledforgenerationofanewsessionID.Thefunction

providedshouldreturnastringwhichwillbeusedasthesessionID.“req”isgiventothe

functionasthefirstargumentincasethereisaneedforavaluetobeattachedtothe“req”

whentheIDisbeinggenerated.Thedefaultvalueforthiswillbeafunctionwhichcanuse

“uid2”forthegenerationoftheIDs.

Note:Toavoidconflictionofthesessions,makesurethatthegeneratedIDsareunique,

thatis,theyshouldbedifferentfromeachother.Considertheexamplegivenbelowwhich

showshowthiscanbedone:

application.use(session({

genid:function(req){

returngenuuid()//usingUUIDsforthesessionIDs

},

secret:‘mysecret‘

}))

Name

ThisisthenameofthesessionIDcookiewhichistobesetintheresponse.Notethatitis

readfromtherequest.Thedefaultvalueforthisisthe“connect.sid.”Forthosewhohave

multipleappswhicharerunningonthesamehost,thenthesessioncookieshavetobe

separatedfromeachother.Toachievethis,onehastosetdifferentnamesineachofthe

apps.

Proxy

Wheneveryouaresettingsecurecookies,youhavetotrustthereverseproxy.Thiscanbe

doneviatheheaderfor“X-Forwarded-Proto.”Thedefaultvalueforthisis“undefined.”

Thepossiblevaluesforthisareexplainedbelow:

1. “true”-theheader“X-Forwarded-Proto”willbeused.

2. “false”-alloftheheaderswillbeignored,andtheconnectionwillbeconsidered

onlyifadirect“TLS/SSL”connectionexists.

3. “Undefined”-thiswillusethesettingsfor“trustproxy”fromtheExpressitself.

Resave

Thiswillforcethesessiontobesavedbacktothesessionstore.Thishappenswhetheror

notthesessionwasmodifiedduringtherequest.Thenecessityofthiswilldependonyour

sessionstore.However,ifaclientmakesparallelrequests,raceconditionsmaybecreated.

Rolling

Thecookiewillbeforcedtobesetoneachoftheresponses.Theexpirationdateisalso

reset.Thedefaultvalueforthisis“false.”

saveUninitialized

Withthis,asessionwhichwasnotinitializedwillbesavedtothesessionstore.An

uninitializedsessionisonewhichisnewandnotmodifiedinanyway.Thedefaultsetting

forthisis“true.”However,thishasdeprecatedandisexpectedtochangeinthefuture.

Requiredoption

ThisisthesecretwhichisusedforsigningthecookieforthesessionID.Itcanbemade

upofanarrayofsecretsorastringjustforasinglesecret.Incaseyouprovideanarrayof

secrets,onlythefirstelementinthearraywillbeusedforsigningthecookieforthe

sessionID.Therestoftheelementswillbeusedforverificationofthesignaturein

requests.

Store

Thisistheinstanceofthesessionstore.Itsdefaultisanew“MemoryStore”instance.

Considertheexamplegivenbelow:

varapplication=express()

application.set(‘trustproxy’,1)//trustingthefirstproxy

application.use(session({

secret:‘mysecret’,

resave:false,

saveUninitialized:true,

cookie:{secure:true}

}))

Weneedtobeabletousethecookiesinaproductionenvironment,andatthesametime

allowfortestinginadevelopmentenvironment.Thesetupcanbeenabledbyuseofthe

“NODE_ENV.”Considertheexamplegivenbelow,whichshowshowthiscanbedone:

varapplication=express()

varsession={

secret:‘mysecret‘,

cookie:{}

}

if(application.get(‘env’)===‘production’){

application.set(‘trustproxy’,1)//trustingthefirstproxy

session.cookie.secure=true//servingsecurecookies

}

application.use(session(session))

Thedefaultsettingfor“cookie.maxAge”is“null,”anditwillneverexpire,whichmeans

thatthecookiewillbecomeabrowser-sessioncookie.Thecookieisonlyremovedonce

theuserhasclosedthebrowser.Thesessionisalsoremoved.

req.session

Forsessiondatatobestoredandaccessed,youshouldusetheproperty“req.session,”and

thestoreinitializesthisasaJSON.Thesessionobjectswillthenbeleftfine.Considerthe

examplegivenbelow,whichshowsaviewcounterwhichisspecifictoauser:

application.use(session({secret:‘mysecret‘,cookie:{maxAge:50000}}))

application.use(function(req,res,next){

varsession=req.session

if(session.views){

session.views++

res.setHeader(‘Content-Type’,‘text/html’)

res.write(‘<p>views:‘+session.views+‘</p>’)

res.write(‘<p>willexpiresin:‘+(session.cookie.maxAge/1000)+‘s</p>’)

res.end()

}else{

session.views=1

res.end(‘Thisisademoforsessions.Refreshthepage!’)

}

})

Session.regenerate()

Thismethodisinvokedwhenwewanttogeneratethesession.Afterthis,anewsession

instanceandSIDwillbeinitializedatthe“req.session.”Thisisshownbelow:

req.session.regenerate(function(error){

//anewsessionshouldbeaddedhere

})

Session.destroy()

Withthis,thesessionisdestroyed,andthe“req.session”removed.Itwillthenbe

regeneratedinthenextrequest.Thisisshownbelow:

req.session.destroy(function(error){

//asessioncannotbeaccessedhere.

})

Session.reload()

Thisisusedforreloadingthesessionasshownbelow:

req.session.reload(function(error){

//thesessionhasbeenupdated

})

Session.save()

Thisisforsavingthesessionasshownbelow:

req.session.save(function(error){

//sessionhasbeensaved

})

Considertheexamplegivenbelow,whichusesthe“express-session”soastostorethe

pageviewsfortheuser:

varexpress=require(‘express’)

varpurl=require(‘parseurl’)

varsession=require(‘express-session’)

varapplication=express()

application.use(session({

secret:‘mysecret‘,

resave:false,

saveUninitialized:true

}))

application.use(function(req,res,next){

varvws=req.session.views

if(!vws){

vws=req.session.views={}

}

//gettingtheurlpathname

varpathname=purl(req).pathname

//countingtheviews

vws[pathname]=(vws[pathname]||0)+1

next()

})

application.get(‘/foo’,function(req,res,next){

res.send(‘youhaveviewedthispage‘+req.session.vws[‘/test’]+‘times’)

})

application.get(‘/bar’,function(req,res,next){

res.send(‘youhaveviewedthispage‘+req.session.vws[‘/bar’]+‘times’)

})

ThatishowsessionscanbeusedinExpressJS.

Chapter3-serve-index

Thisisusedforservingpageshavinglistingsofadirectorytoaparticularpath.Itcanbe

installedbyexecutingthecommandgivenbelow:

$npminstallserve-index

Theabovecommandwillinstallthe“serve-index”toyourcomputer.Touseitinyour

program,ithastobeincludedorcalledbyuseofthe“require”method.Thisisshown

below:

varsvIndex=require(‘serve-index’)

TheAPIwillthenbeincludedinyourprogram.

serveIndex(path,options)

Thiswillreturnthemiddlewarewhichservestheindexofthedirectoryinthe“path”you

havegiven.Thepathhereisbasedoffofthevaluefor“req.url.”Foryoutochangethe

URLbase,makeuseofthe“app.use.”

Thefollowingpropertiesareacceptedbytheserveindexintheoptionsobject:

Filter

Thisfilterfunctionisappliedtofiles.Itsdefaultvalueis“false.”Itiscalledforeachofthe

files,anditusesthesignature“filter(filename,index,files,dir).”“Filename”willbethe

file’sname,“index”willbethearrayindex,and“files”isthearrayofthefiles,while

“dir”willbetheabsolutepathinwhichthefileislocated.

Hidden

Thisisusedfordisplayingthehiddenfiles.Itsdefaultvalueis“false.”

Icons

Thisisfordisplayingicons.Itdefaultvalueis“false.”

Stylesheet

ThisisanoptionalpathwhichleadstotheCSSstylesheet.Itsdefaultvalueisthebuilt-in

stylesheet.

Template

ThisisanoptionalpathwhichleadstoanHTMLtemplate,andisusedforrenderingthe

HTMLstring.

View

Thisisthedisplaymode.

Considertheexamplegivenbelow,whichshowshowalltheabovecanbeused:

varfhandler=require(‘finalhandler’)

varhttp=require(‘http’)

varsvIndex=require(‘serve-index’)

varsvStatic=require(‘serve-static’)

//TheServedirectoryworkstoindexeforpublic/ftpfolder(havingicons)

varindex=svIndex(‘public/ftp’,{‘icons’:true})

//Servingupthepublic/ftpfolderfiles

varserve=svStatic(‘public/ftp’)

//Creatingaserver

varserver=http.createServer(functiononRequest(req,res){

vardone=fhandler(req,res)

serve(req,res,functiononNext(error){

if(error)returndone(error)

index(req,res,done)

})

})

//Listen

server.listen(3000)

Toservethedirectoryindexeswithexpress,dothefollowing:

varexpress=require(‘express’)

varsvIndex=require(‘serve-index’)

varapplication=express()

//ServingURLslikethe/ftp/thingaspublic/ftp/thing

application.use(‘/ftp’,svIndex(‘public/ftp’,{‘icons’:true}))

application.listen()

Chapter4-cookie-Sessions

Thisisamodulewhichisusedforprovidingguestsessionssothateachofthevisitorswill

haveasession,whetherauthenticatedornot.Incasethesessionisnew,theproperty“Set-

Cookie”willbeproduced,regardlessofwhetheryouarepopulatingthesession.

Itcanbeinstalledbyuseofthefollowingcommand:

$npminstallcookie-session

FortheAPItobeusedintheprogram,wehavetousethe“require”commandasshown

below:

varcookieSession=require(‘cookie-session’)

Thefollowingoptionsareacceptedinthecookiesessionintheoptionsobject:

Name

Thisisthenameofthecookiewhichistobeset.Itsdefaultvalueis“session”.

Keys

Thisisthelistofthekeystobeusedforsigningandverifyingthecookievalues.Cookies

whichhavebeensetarealwayssignedwiththe“keys[0].”Therestofthekeyswillthen

bevalidforthepurposeofverification,andthiswillallowfortherotationtobedone.

Secret

Thisisastringwhichwillbeusedasasecretkeyincasethe“keys”arenotprovided.

Thereisalsoanumberofcookieoptionswhichyouneedtoknowhowtouse.

Ifyouneedtodestroyaparticularsession,doitasfollows:

req.session=null

Considerthesimpleviewcounterexamplegivenbelow.Hereistheexample:

varcookieSession=require(‘cookie-session’)

varexpress=require(‘express’)

varapplication=express()

appliation.set(‘trustproxy’,1)//trustingthefirstproxy

application.use(cookieSession({

name:‘session’,

keys:[‘key1’,‘key2’]

}))

application.use(function(req,res,next){

//Updatingtheviews

req.session.views=(req.session.views||0)+1

//Writingtheresponse

res.end(req.session.views+‘views’)

})

application.listen(3000)

Considerthenextexamplegivenbelow:

varcookieSession=require(‘cookie-session’)

varexpress=require(‘express’)

varapplication=express()

application.set(‘trustproxy’,1)//trustingthefirstproxy

application.use(cookieSession({

name:‘session’,

keys:[‘key1’,‘key2’]

}))

//Thiswillallowyoutosetreq.session.maxAgeforlettingcertainsessions

//haveadifferentvalueotherthanthedefaultone.

application.use(function(req,res,next){

req.sessionOptions.maxAge=req.session.maxAge||req.sessionOptions.maxAge

})

//…thelogicshouldbeaddedhere…

Youhavetonotethattheentiresessionobjectwillbeencodedandstoredinacookie.The

maximumcookiesizelimitonthedifferentbrowserscanthenbeexceeded.Ifthesession

objectislargeenoughanditcanexceedthelimitofthebrowserwhenithasbeenencoded,

whatwillhappeninmostcasesisthatthebrowserwillrefuseoravoidstoringthecookie.

Chapter5-MorganinExpressJS

ThisisloggermiddlewarefortheHTTPrequestforNode.js.TousetheAPIinyour

program,youhavetousethe“require”keywordasshownbelow:

varmorgan=require(‘morgan’)

Thefollowingformatisusedforcreatingthis:

morgan(format,options)

Asshownintheaboveformat,wehavetwoparametersorarguments.

ThefollowingpropertiesareacceptedbyMorganintheoptionsobject:

Immediate

Theloglineshouldbewrittenonrequestratherthanonresponse.Thiswillmeanthatthe

requestswillalwaysbeloggedeveniftheserveritselfcrashes,butitwillbeimpossible

forustologthedatafromtheresponse.

Skip

Thisisafunctionusedforthedeterminationofwhetherornotloggingwasskipped.The

defaultvalueforthisis“false,”Considertheexamplegivenbelow,whichshowshowthe

functioncanbecalled:

//EXAMPLE:onlythelogerrorresponses

morgan(‘combined’,{

skip:function(req,res){returnres.statusCode<400}

})

Stream

Thisisanoutputstreamwhichisusedforwritingloglines,anditsdefaultvalueis

“process.stdout.”

Considertheexamplegivenbelow,whichshowshowalltherequestscanbeloggedinthe

ApachecombinedformattotheSTDOUT.Hereistheexample:

varexpress=require(‘express’)

varmorgan=require(‘morgan’)

varapplication=express()

application.use(morgan(‘combined’))

application.get(‘/’,function(req,res){

res.send(‘hello,there!’)

})

vanillahttpserver

Anexamplewhichdemonstrateshowthiscanbedoneisgivenbelow:

varfhandler=require(‘finalhandler’)

varhttp=require(‘http’)

varmorgan=require(‘morgan’)

//creatingthe“middleware”

varlogger=morgan(‘combined’)

http.createServer(function(req,res){

vardone=finalhandler(req,res)

logger(req,res,function(error){

if(error)returndone(error)

//respondingtotherequest

res.setHeader(‘content-type’,‘text/plain’)

res.end(‘hello,there!’)

})

})

WritingLogstoaFile

Considertheexamplegivenbelow,whichshowshowtherequestscanbeloggedin

Apachecombinedformattoourfile“access.log”:

varexpress=require(‘express’)

varfs=require(‘fs’)

varmorgan=require(‘morgan’)

varapplication=express()

//creatingawritestream(intheappendmode)

varaLogStream=fs.createWriteStream(__dirname+‘/access.log’,{flags:‘a’})

//settingupthelogger

application.use(morgan(‘combined’,{stream:aLogStream}))

application.get(‘/’,function(req,res){

res.send(‘hello,there!’)

})

logfilerotation

Intheexamplegivenbelow,theappwilllogalltherequestsintheApachecombined

formattoanyofthelogfilesinourdirectory“log/”byuseofthefile-stream-rotator

module.Theexampleisasfollows:

varFStreamRotator=require(‘file-stream-rotator’)

varexpress=require(‘express’)

varfs=require(‘fs’)

varmorgan=require(‘morgan’)

varapplication=express()

varlDirectory=__dirname+‘/log’

//ensuringthelogdirectoryexists

fs.existsSync(lDirectory)||fs.mkdirSync(lDirectory)

//creatingarotatingwritestream

varaLogStream=FStreamRotator.getStream({

filename:lDirectory+‘/access-%DATE%.log’,

frequency:‘daily’,

verbose:false

})

//settingupthelogger

application.use(morgan(‘combined’,{stream:aLogStream}))

application.get(‘/’,function(req,res){

res.send(‘hello,there!’)

})

Customtokenformats

Inthenextapp,wewillusethecustomtokenformats.ItworksbyaddinganIDtoallof

therequests,andwillthendisplayitbyuseofthe“:id”token.Hereistheapp:

varexpress=require(‘express’)

varmorgan=require(‘morgan’)

varid=require(‘node-uuid’)

morgan.token(‘id’,functiongetId(req){

returnreq.id

})

varapplication=express()

application.use(assignid)

app.use(morgan(‘:id:method:url:response-time’))

app.get(‘/’,function(req,res){

res.send(‘hello,world!’)

})

functionassignId(req,res,next){

req.id=uuid.v4()

next()

}

Chapter6-CORS

ThisisaNode.jspackagewhichprovidesanExpressJS/Connectmiddlewarewhichcanbe

usedforenablingofthevariousoptionsforCORS.

Toinstallitvianpmcommand,executethecommandgivenbelow:

$npminstallcors

Thiscanbeusedasshownbelow:

varexpress=require(‘express’)

,cors=require(‘cors’)

,application=express();

application.use(cors());

application.get(‘/products/:id’,function(req,res,next){

res.json({msg:‘ThishasCORSenabledforalltheorigins!’});

});

application.listen(80,function(){

console.log(‘webserverwhichisCORSenabledlisteningonport80’);

});

ToenableCORSforasingleroute,doitasfollows:

varexpress=require(‘express’)

,cors=require(‘cors’)

,application=express();

application.get(‘/products/:id’,cors(),function(req,res,next){

res.json({msg:‘ThishastheCORSenabledforalltheorigins!’});

});

application.listen(80,function(){

console.log(‘webserverwhichisCORSenablednowlisteningonport80’);

});

ToconfiguretheCORS,doitasfollows:

varexpress=require(‘express’)

,cors=require(‘cors’)

,application=express();

varcOptions={

origin:‘http://sample.com’

};

application.get(‘/products/:id’,cors(cOptions),function(req,res,next){

res.json({msg:‘ThishasCORSenabledonlyforsample.com.’});

});

application.listen(80,function(){

console.log(‘webserverwhichisCORS-enabledisnowlisteningonport80’);

});

ConfigurationofCORSw/DynamicOrigincanbedoneasfollows:

varexpress=require(‘express’)

,cors=require(‘cors’)

,application=express();

varwhitelist=[‘http://sample1.com’,‘http://sample2.com’];

varcOptions={

origin:function(origin,callback){

varorIsWhitelisted=whitelist.indexOf(origin)!==-1;

callback(null,orIsWhitelisted);

}

};

application.get(‘/products/:id’,cors(cOptions),function(req,res,next){

res.json({msg:‘ThishasCORSenabledforthewhitelisteddomain.’});

});

application.listen(80,function(){

console.log(‘CORS-enabledwebserverlisteningonport80’);

});

HowtoenableCORSPre-Flight

CertainrequestsforCORSareconsideredtobecomplex,andtheseneedaninitial

OPTIONSrequest.ACORSrequestwhichusestheHTTPverbisconsideredtobe

complexcomparedtotheonewhichusesPOST/GET/HEADortheoneusingcustom

headers.Forpre-fightingtobeenabled,anewOPTIONShandlerhastobeaddedforthe

routewhichneedstobesupported.Thisisshownbelow:

varexpress=require(‘express’)

,cors=require(‘cors’)

,application=express();

application.options(‘/products/:id’,cors());//enablingapre-flightrequestfortheDELETErequest

application.del(‘/products/:id’,cors(),function(req,res,next){

res.json({msg:‘ThishasCORSenabledforalltheorigins!’});

});

application.listen(80,function(){

console.log(‘ThewebserverwhichisCORS-enabledislisteningonport80’);

});

Pre-flightcanalsobeenabledacrosstheboardasshownbelow:

application.options(‘*’,cors());//includingbeforetheotherroutes

AsynchronousconfigurationofCORS

varexpress=require(‘express’)

,cors=require(‘cors’)

,application=express();

varwhitelist=[‘http://sample1.com’,‘http://sample2.com’];

varcOptionsDelegate=function(req,callback){

varcOptions;

if(whitelist.indexOf(req.header(‘Origin’))!==-1){

cOptions={origin:true};//reflecting(enabling)therequestedorigininourCORSresponse

}else{

cOptions={origin:false};//disablingtheCORSforourrequest

}

callback(null,cOptions);//callbackneedstwoparameters:errorandtheoptions

};

application.get(‘/products/:id’,cors(cOptionsDelegate),function(req,res,next){

res.json({msg:‘ThishasCORSenabledforthewhitelisteddomain.’});

});

application.listen(80,function(){

console.log(‘webserverwithCORSenabledislisteningonport80’);

});

Thatishowitcanbedone.

Chapter7-Express-Paginate

Thisistobeusedtogetherwiththepaginationpluginsfordatabasessuchasthe

MongoDB.

Toinstall,executethecommandgivenbelow:

npminstall-Sexpress-paginate

Forittobeusedintheprogram,onehastousethe“require”keywordsoastoincludeit

intotheprogramThisisshownbelow:

varpaginate=require(‘express-paginate’);

With“paginate,”anewinstanceof“express-paginate”willbecreated.Considerthe

examplegivenbelow:

//#app.js

varexpress=require(‘express’);

varpaginate=require(‘express-paginate’);

varapplication=express();

//keepingthisbeforealltheroutesthatwillusepagination

application.use(paginate.middleware(10,50));

application.get(‘/users’,function(req,res,next){

//weareassumingthat`Users`waspreviouslydefinedinourexample

//as`varUsers=database.model(‘Users’)`forthoseusing`mongoose`

//andthattheMongooseplugin`mongoose-paginate`hasbeenadded.

//tothemodelforUsersviathe`User.plugin(require(‘mongoose-paginate’))`

Users.paginate({},{page:req.query.page,limit:req.query.limit},function(error,

users,pageCount,itemCount){

if(error)returnnext(error);

res.format({

html:function(){

res.render(‘users’,{

users:users,

pageCount:pageCount,

itemCount:itemCount

});

},

json:function(){

//CreatedbytheAPIresponseforlistobjects

res.json({

object:‘list’,

has_more:paginate.hasNextPages(req)(pageCount),

data:users

});

}

});

});

});

application.listen(3000);

Thesecondcodefortheappshouldbeasfollows:

//-users.jade

h1Users

//-alinkforsortingbynamewillbecreatedbythis

//-youmusthavenoticedthatweonlyhavetopassthequerystringparam

//-whichistobemodifiedhere,butnottheentirequerystring

a(href=paginate.href({sort:‘name’}))Sortingbyname

//-thiswillassumethatyouhave`?age=1`or`?age=-1`inthequerystring

//-sothevalueswillbenegatedbythisandyouwillbegiven

//-anoppositesortingorder(thatis,descwith-1orascwith1)

a(href=paginate.href({sort:req.query.age===‘1’?-1:1}))Sortbyage

ul

eachmyuserinusers

li=myuser.email

include_paginate

Thethirdcodeshouldbeasfollows:

//-_paginate.jade

//-Inthisexample,wewillmakeuseoftheBootstrap3.xpaginationclasses

ifpaginate.hasPreviousPages||paginate.hasNextPages(pageCount)

.navigation.well-sm#pagination

ul.pager

ifpaginate.hasPreviousPages

li.previous

a(href=paginate.href(true)).prev

i.fa.fa-arrow-circle-left

|Previous

ifpaginate.hasNextPages(pageCount)

li.next

a(href=paginate.href()).next

|Next&nbsp;

i.fa.fa-arrow-circle-right

Chapter8-Multer

ThisismiddlewareinNode.jswhichisusedtohandle“multipart/form-data.”Thisisused

forthepurposeofuploadingfilestotheserver.Tomaximizeitsefficiency,itisbuilton

topof“busboy.”Youhavetonotethatanyformwhichisnotmultipartcannotbehandled

byMulter.

Theinstallationofthiscanbedonebyexecutionofthefollowingcommand:

$npminstall—savemulter

Itworksbyaddinga“body”anda“file/files”objecttothe“request”object.Inthe“body”

object,thevaluesfortheformfieldswillbestored.The“file/files”objectwillcontainthe

fileswhichhavebeenuploadedtotheserver.

Considertheexamplegivenbelowwhichshowshowthiscanbedone:

varexpress=require(‘express’)

varmulter=require(‘multer’)

varuploadfile=multer({dest:‘uploads/’})

varapplication=express()

application.post(‘/profile’,uploadfile.single(‘avatar’),function(req,res,next){

//req.fileisour`avatar`file

//req.bodyisforholdingthetextfields,ifanyareavailable

})

application.post(‘/photos/upload’,uploadfile.array(‘photos’,12),function(req,res,next){

//req.filesisanarrayof`photos`forfiles

//req.bodywillcontainthetextfields,iftherewereany

})

varcUpload=uploadfile.fields([{name:‘avatar’,maxCount:1},{name:‘gallery’,maxCount:8}])

application.post(‘/cool-profile’,cUpload,function(req,res,next){

//req.filesisourobject(String->Array)wherefieldnameisourkey,andthevalueisanarrayofthefiles

//

//example

//req.files[‘avatar’][0]->File

//req.files[‘gallery’]->Array

//

//req.bodywhichcontainsthetextfields,ifanywereavailable

})

Forthosewhoareinneedofhandlingatextwhichisinmultipartform,anyoftheMulter

methodscanbeused.Thesemethodsincludethe“single(),”“.array(),”and“fields().”

Considertheexamplegivenbelow,whichshowshowthe“.array()”canbeused:

varexpress=require(‘express’)

varapplication=express()

varmulter=require(‘multer’)

varuploadfile=multer()

application.post(‘/profile’,uploadfile.array(),function(req,res,next){

//req.bodyhasourtextfields

})

WithMulter,anoptionsobjectisaccepted,inwhichthemostbasiconeisour“dest”

property,anditspecifiesthedestinationofouruploadedfiles.Iftheoptionsobjectis

omitted,thefileswhichyouuploadwillbekeptinthememoryotherthaninthedisk.

Toavoidconflictsbroughtbynaming,theMulterwillrenamethefilesandthisisits

defaultsetting.Therestofthefunctioncanbecustomizedaccordingtowhatyouneed.

ThereexistsavarietyofoptionswhichcanbepassedtotheMulter,somakesurethatyou

understandhowthesecanbepassed.

Inanormalwebapplication,onlythe“dest”propertymightberequired,andthiscanbe

configuredasshownbelow:

varuploadfile=multer({dest:‘uploads/’})

Forthosewhoareinneedofexercisingagreatercontrolonyouruploadedfiles,justuse

the“storage”propertyotherthanthe“dest”property.“DiskStorage”and

“MemoryStorage”storageenginesareshippedwithMulter.Youcanusethirdpartiessoas

toaccessmorestorageengines.

Ifyouneedtoexercisefullcontrolofyourfileswhicharestoredonthedisk,usethedisk

storageengine.Thisisshownbelow:

varstorage=multer.diskStorage({

destination:function(req,file,cb){

cb(null,‘/tmp/file-uploads’)

},

filename:function(req,file,cb){

cb(null,file.fdname+‘-‘+Date.now())

}

})

varuploadfile=multer({storage:storage})

Theonlytwooptionswhichareavailableincludethe“filename”and“destination.”They

arethefunctionswhichdeterminehowthefilesaretobestored.The”destination”

propertywilldeterminethefolderinthedirectoryinwhichtheuploadedfileistobe

stored.Thiscanalsobespecifiedasapathintheprogram.Ifthispropertyisnot

specified,thenthedefaultpathisusedintheoperatingsystem.

FileFilter

Thispropertycanbeusedforsettingthefileswhicharetobeuploadedandtheoneswhich

aretobeskipped.Thisfunctionshouldbeusedasshownintheexamplegivenbelow:

functionfileFilter(req,file,cb){

//Thefunctionwillcallthe`cb`withaboolean

//toindicatethatthefileshouldbeaccepted

//ifthefileistoberejected,pass`false`,likeso:

cb(null,false)

//forthefiletobeaccepted,pass`true`,likeso:

cb(null,true)

//youcanpassanerrorsincesomethingmaygowrongatsomepoint:

cb(newError(‘Ihavenoclue!’))

}

ErrorHandling

Whenanerrorhasbeenencountered,theMulterwillpassittoExpress.Thestandard

Expresserrorwaycanbeusedforthepurposeofdisplayinganerror.

ForyoutocatchtheerrorswhichareoriginatingfromtheMulter,justcallthemiddleware

functiononyourown.Thisisshownintheexamplegivenbelow:

varuploadfile=multer().single(‘avatar’)

application.post(‘/profile’,function(req,res){

uploadfile(req,res,function(error){

if(error){

//Anerrorhasoccurredwhenuploading

return

}

//Everythingwasokay

})

})

Thatishowitcanbeused.

Chapter9-Compression

ThisismiddlewareavailableinNode.js.Itsupportsthefollowingcompressioncodes:

deflate

gzip

Toinstallthismiddlewareinyoursystem,executethefollowingcommand:

$npminstallcompression

ToincludethisAPIinyourprogram,usethe“require”keywordasshownbelow:

varcompression=require(‘compression’)

Therearedifferentoptionswhichcanbeusedsoastoreturnthecompressionmiddleware.

.filter

Thisisthedefaultfilterfunction.Itisusedforconstructionofacustomfilterfunction

whichwillbeanextensionofourdefaultfunction.Theexamplegivenbelowshowshow

thiscanbeused:

application.use(compression({filter:compress}))

functioncompress(req,res){

if(req.headers[‘x-no-compression’]){

//responseshavingthisheaderrequestshouldnotbecompressed.

returnfalse

}

//fallbacktostandardfilterfunction

returncompression.filter(req,res)

}

red.flush()

Withthismodule,theresponsewhichhasbeencompressedpartiallyisflushedtothe

client.Letusgiveexamplesofthese.

express/connect

Thismodulecanbeusedbyuseofthe“app.use,”whichisavailableineitherExpressand

connect.Requestspassedthroughthemiddlewarearealwayscompressed.Considerthe

examplegivenbelowwhichshowshowthiscanbedone:

varcompression=require(‘compression’)

varexpress=require(‘express’)

varapplication=express()

//compressingalloftherequests

application.use(compression())

//addingalltheroutes

Thatishowitcanbedone.

Server-SentEvents

Theworkingofthismodulewithserver-sideisnotdoneoutofthebox.Forcontenttobe

compressed,awindowfortheoutputhastobebufferedupsothatwecangetagood

compression.

Todoallthis,wehavetocallthe“red.flush()”forthosewhoneedthedatawrittensoasto

makeittoourclient.Thisisshownbelow:

varcompression=require(‘compression’)

varexpress=require(‘express’)

varapplication=express()

//compressingtheresponses

application.use(compression())

//theserver-senteventstream

application.get(‘/events’,function(req,res){

res.setHeader(‘Content-Type’,‘text/event-stream’)

res.setHeader(‘Cache-Control’,‘no-cache’)

//sendingapingapproxafterevery2seconds

vartimer=setInterval(function(){

res.write(‘data:ping\n\n’)

//!!!ourmostimportantpartfortheprogram

res.flush()

},2000)

res.on(‘close’,function(){

clearInterval(timer)

})

})

Chapter10-csurf

ThisisatokenmiddlewareforCSRF.Itactsasamiddlewareforprotectionpurposes.For

ittobeused,onehastobeginbyinitializingacookie-parserorasessionmiddleware.It

canbeinstalledintoone’scomputerbyexecutingthefollowingcommand:

$npminstallcsurf

TousetheAPIinyourprogram,usethe“require”commandasshownbelow:

varcsurf=require(‘csurf’)

Thatishowitcanbeincludedintotheprogram.

Theoptionsforthismoduletakemultipleanddifferentobjectswhichyoucanlearnhow

touse.

Considertheexamplegivenbelow,whichshowsacodefortheserver-sidewhichcanbe

usedforgenerationoftheCSRFformwhichcanbeusedforpostingback.Thisisthe

example:

varcParser=require(‘cookie-parser’)

varcsrf=require(‘csurf’)

varbParser=require(‘body-parser’)

varexpress=require(‘express’)

//settinguptheroutemiddlewares

varcsrfProtection=csrf({cookie:true})

varpForm=bParser.urlencoded({extended:false})

//creatinganexpressapp

varapplication=express()

//parsingcookies

//thisisneededbecause“cookie”istrueinthecsrfProtection

application.use(cParser())

application.get(‘/form’,csrfProtection,function(req,res){

//passingthecsrfTokentoourview

res.render(‘send’,{csrfToken:req.csrfToken()})

})

application.post(‘/process’,pForm,csrfProtection,function(req,res){

res.send(‘Thedataisnowbeingprocessed’)

})

Insideyourview,thevalueforcsrfTokenshouldbesettothevalueofahiddeninputfield

“_csrf.”Thisisshownbelow:

<formaction=”/process”method=“POST”>

<inputtype=“hidden”name=“_csrf”value=”{{csrfToken}}”>

Bestcolor:<inputtype=“text”name=“bestColor”>

<buttontype=“submit”>Submit</button>

</form>

Thatishowsimplyitcanbedone.

IgnoringtheRoutes

InAPIareasforthewebsitesinwhichwewillhaveourrequestsfullyauthenticated,the

CSRFshouldbedisabled.APIroutingcanbeignoredbytheuseofroutersandExpress.

Considertheexamplegivenbelow,whichshowshowthiscanbedone:

varcParser=require(‘cookie-parser’)

varcsrf=require(‘csurf’)

varbParser=require(‘body-parser’)

varexpress=require(‘express’)

//settinguptheroutemiddlewares

varcsrfProtection=csrf({cookie:true})

varpForm=bParser.urlencoded({extended:false})

//creatinganexpressapp

varapplication=express()

//parsingcookies

//thisisneededbecause“cookie”istrueinthecsrfProtection

application.use(cParser())

//creatinganapirouter

varapi=createApiRouter()

//mountingtheapibeforethecsrfisappendedtoourappstack

application.use(‘/api’,api)

//addingthecsrf,afterthe“/api”hasbeenmounted

appliation.use(csrfProtection)

application.get(‘/form’,function(req,res){

//passingthecsrfTokentoourview

res.render(‘send’,{csrfToken:req.csrfToken()})

})

application.post(‘/process’,pForm,function(req,res){

res.send(‘csrfwasrequiredforgettinghere’)

})

functioncreateApiRouter(){

varrouter=newexpress.Router()

router.post(‘/getProfile’,function(req,res){

res.send(‘thereisnocsrfheretoget’)

})

returnrouter

}

Thatishowitcanbedone.

Customerrorhandling

WhenthevalidationoftheCSRFhasfailed,anerrorwith“err.code===

‘EBADCSRFTOKEN’”willbethrown.Thiscanalsobeusedsoastodisplayerror

messages.Considertheexamplegivenbelow,whichshowshowthiscanbedone:

varbParser=require(‘body-parser’)

varcParser=require(‘cookie-parser’)

varcsrf=require(‘csurf’)

varexpress=require(‘express’)

varapplication=express()

application.use(bParser.urlencoded({extended:false}))

application.use(cParser())

application.use(csrf({cookie:true}))

//theerrorhandler

application.use(function(error,req,res,next){

if(error.code!==‘EBADCSRFTOKEN’)returnnext(error)

//handlingtheCSRFtokenerrorsisdonehere

res.status(403)

res.send(‘Theformwastamperedwith’)

})

Thatishowitcanbedone.

Chapter11-body-parser

ThisistheNode.jsmiddlewareforbodyparsing.However,itdoesnothandlemultipart

bodiesbecauseoftheirlargeandcomplexnature.Whendealingwithmultipartbodies,

youmighthavetodealwiththefollowingmodules:

multer

busboyandconnect-busboy

formidable

multipartyandconnect-multiparty

Themoduleprovidestheuserwiththefollowingparsers:

URL-encodedformbodyparser

Rawbodyparser

JSONbodyparser

Textbodyparser

Toinstallit,justexecutethefollowingcommand:

$npminstallbody-parser

TousetheAPI,includeitinyourprogrambyuseofthe“require”command.Thisis

shownbelow:

varbParser=require(‘body-parser’)

Withtheobject“bParser,”variousfactoriesareexposedforthepurposeofcreationof

middlewares.Theproperty“req.body”willbepopulatedbyallmiddlewaresbyuseofthe

parsedbodyoranerrorwillbeparsedtothecallback.

InExpress,agenericJSONandURL-encodedparsercanbeaddedasatop-level

middleware.Withthis,thebodiesofalltheincomingrequestswillbeparsed.Considerthe

simpleexamplegivenbelow,whichshowshowthiscanbedone:

varexpress=require(‘express’)

varbParser=require(‘body-parser’)

varapplication=express()

//parsingtheapplication/x-www-form-urlencoded

application.use(bParser.urlencoded({extended:false}))

//parsingtheapplication/json

application.use(bParser.json())

application.use(function(req,res){

res.setHeader(‘Content-Type’,‘text/plain’)

res.write(‘youposted:\n’)

res.end(JSON.stringify(req.body,null,2))

})

expressroute-specific

Bodyparserscanbeaddedtotherouteswhichneedthem.ThisispossibleinExpressand

itcaneasilybedone.Thisisthemosteasyandrecommendedwaythatthebody-parser

canbeusedinExpress.Considertheexamplegivenbelow,whichshowshowthiscanbe

done:

varexpress=require(‘express’)

varbParser=require(‘body-parser’)

varapplication=express()

//creatinganapplication/jsonparser

varjParser=bodyParser.json()

//creatinganapplication/x-www-form-urlencodedparser

varurlenParser=bParser.urlencoded({extended:false})

//POST/loginwhichwillgettheurlencodedbodies

application.post(‘/login’,urlenParser,function(req,res){

if(!req.body)returnres.sendStatus(400)

res.send(‘welcome,‘+req.body.username)

})

//POST/api/userswillgettheJSONbodies

application.post(‘/api/users’,jParser,function(req,res){

if(!req.body)returnres.sendStatus(400)

//createauserinthereq.body

})

Changingthecontenttypeforparsers

Withallparsers,atypeoptionisacceptedandwiththis,thecontent-typewillbe

changeableandthisshouldbetheonetobeparsedbythemiddleware.Considerthe

examplegivenbelow,whichshowshowthiscanbedone:

//parsingthevariousanddifferentcustomJSONtypesasaJSON

application.use(bodyParser.json({type:‘application/*+json’}))

//parsingacustomthingintotheBuffer

application.use(bParser.raw({type:‘application/vnd.custom-type’}))

//parsingtheHTMLbodyintothestring

application.use(bParser.text({type:‘text/html’}))

Chapter12-Flash

ThisisthesimplestmannerinwhichExpresscanbeimplemented.Toinstallit,execute

thefollowingcommand:

npmiflash

Considertheexamplegivenbelow,whichshowshowthiscanbedone:

application.use(session());//thesessionmiddleware

application.use(require(‘flash’)());

application.use(function(req,res){

//flashingamessage

req.flash(‘info’,‘hellothere!’);

next();

})

Considerthesecondexamplegivenbelow:

formsgeinflash

a.alert(class=‘alert-‘+msge.type)

p=message.msge

Hereisthefinalexample:

whilemsge=flash.shift()//consumingthemessagesasjadehasreadthem

a.alert(class=‘alert-‘+msge.type)

p=message.msge

Anarrayoff

Lashmessagescanbeasshownbelow:

{

“type”:“info”,

“message”:“message”

}

method-override

ThisisusedforoverridingHTTPverbs.Withit,onecanuseHTTPverbssuchas

“DELETE”and“PUT”inplaceswheretheyarenotsupportedbytheclient.Toinstallitin

yoursystem,executethefollowingcommand:

$npminstallmethod-override

Forthismoduletobeused,youhavetoknowthatabithastobeusedbeforeanyofthe

moduleswhichareinneedoftherequestmethods.

Usingtheheadertooverride

Fortheheadertobeusedforoverriding,theheadernamehastobespecifiedasastring

argumenttothefunction“methodOverride,”Forthecalltobemade,thePOSTrequesthas

tobesenttotheURLhavingtheheaderastheoverriddenmethod.Considertheexample

givenbelowshowing,howthiscanbedone:

varconnect=require(‘connect’)

varmthdOverride=require(‘method-override’)

//overridingwiththeX-HTTP-Method-Overrideheaderinourrequest

application.use(mthdOverride(‘X-HTTP-Method-Override’))

Considertheexamplegivenbelow,whichshowshowthiscanbeusedwith

“XMLHttpRequest”:

varc=newXMLHttpRequest()

c.onload=onload

c.open(‘post’,‘/resource’,true)

c.setRequestHeader(‘X-HTTP-Method-Override’,‘DELETE’)

c.send()

functiononload(){

alert(‘Theresponsewasobtained:‘+this.responseText)

}

Chapter13-serve-favicon

ThisisaNode.jsmiddlewarewhichisusedforthepurposeofservingfavicons.Afavicon

isjustavisualcuewhichbrowsersandotherclientsoftwareuseforthepurposeof

identifyingasite.

Themodulecanbeinstalledintothesystembyexecutingthefollowingcommand:

npminstallserve-favicon

Considertheexamplegivenbelow,showinghowthiscanbeusedinexpress:

varexpress=require(‘express’);

varfavicon=require(‘serve-favicon’);

varapplication=express();

application.use(favicon(__dirname+‘/public/favicon.ico’));

//Additionofyourroutesshouldbedonehere.

application.listen(3000);

Inconnect,thiscanbedoneasfollows:

varconnect=require(‘connect’);

varfavicon=require(‘serve-favicon’);

varapplication=connect();

application.use(favicon(__dirname+‘/public/favicon.ico’));

//Additionofyourmiddlewareshouldbedonehere,etc.

application.listen(3000);

vanillahttpserver

Thisisatypeofmiddlewarewhichcanbeusedeverywhere,includingoutsideExpress

andconnect.

Theexamplegivenbelowshowshowthiscanbedone:

varhttp=require(‘http’);

varfavicon=require(‘serve-favicon’);

varfnhandler=require(‘finalhandler’);

var_favicon=favicon(__dirname+‘/public/favicon.ico’);

varserver=http.createServer(functiononRequest(req,res){

vardone=fnhandler(req,res);

_favicon(req,res,functiononNext(error){

if(error)returndone(error);

//justcontinuewithprocessingoftherequesthere,etc.

res.statusCode=404;

res.end(‘hello’);

});

});

server.listen(3000);

Chapter14-response-time

Thisisthenode.jsresponsetimeheader.Itworksbycreatingamiddlewareforrecording

theresponsetimeofitsrequestsintheHTTPservers.Theresponsetimeinthiscasewill

bethetimewhentherequesthasenteredthemiddlewaretothetimewhentheheaders

havebeenwrittentotheclient.

Thismodulecanbeinstalledbyexecutingthefollowingcommand:

$npminstallresponse-time

Themodulecanbeincludedintotheprogrambyuseofthe“require”keywordasshown

below:

varrespTime=require(‘response-time’)

Considertheexamplegivenbelow,whichshowshowthiscanbeusedinboththeExpress

andtheconnect:

varexpress=require(‘express’)

varrespTime=require(‘response-time’)

varapplication=express()

application.use(respTime())

application.get(‘/’,function(req,res){

res.send(‘hello,there!’)

})

Thatishowitcanbeused.

vanillahttpserver

Thiscanbeusedasfollows:

varfinalhandler=require(‘finalhandler’)

varhttp=require(‘http’)

varrespTime=require(‘response-time’)

//creatingthe“middleware”

var_responseTime=respTime()

http.createServer(function(req,res){

vardone=fnhandler(req,res)

_responseTime(req,res,function(err){

if(error)returndone(error)

//respondingtotherequest

res.setHeader(‘content-type’,‘text/plain’)

res.end(‘hello,there!’)

})

})

Thatishowthemodulecanbeused.

Responsetimemetris

varexpress=require(‘express’)

varrespTime=require(‘response-time’)

varStatsD=require(‘node-statsd’)

varapplication=express()

varstatistics=newStatsD()

statistics.socket.on(‘error’,function(err){

console.error(err.stack)

})

application.use(respTime(function(req,res,time){

varstat=(req.method+req.url).toLowerCase()

.replace(/[:.]/g,”)

.replace(/\//g,‘_’)

statistics.timing(stat,time)

}))

application.get(‘/’,function(req,res){

res.send(‘hello,there!’)

})

Chapter15-express-namespace

Withthis,namespacedroutingcapabilitiesareaddedtoExpress.Toinstallitintothe

system,onecanexecutethefollowingcommand:

$npminstallexpress-namespace

Considertheexamplegivenbelow,whichcanbeusedforrespondingtoanyofthe

requests.Hereistheexample:

GET/forum/12

GET/forum/12/view

GET/forum/12/edit

GET/forum/12/thread/5

DELETE/forum/12

Forthemoduletobeused,onemustusethe“app.namespace()”and“require(‘express-

namespace’).”Themodulewillthenbemadeavailabletoyou.

Touseit,wehavetopassacallbackfunction,andthenperformaroutingtothemethod.

Aftereachofthecallbacks,theinvocationwillbecompleted,andthenamespacewillbe

storedtogetherwithitsstate.Thisisshownbelow:

application.namespace(‘/forum/:id’,function(){

application.get(‘/(view)?’,function(req,res){

res.send(‘GETforum‘+req.params.id);

});

application.get(‘/edit’,function(req,res){

res.send(‘GETforum‘+req.params.id+‘editthepage’);

});

application.namespace(‘/thread’,function(){

application.get(‘/:tid’,function(req,res){

res.send(‘GETforum‘+req.params.id+‘thread‘+req.params.tid);

});

});

application.del(‘/’,function(req,res){

res.send(‘DELETEtheforum‘+req.params.id);

});

});

Thecurrentnamespacecanalsobeaccessedviathe“app.currentNamespace.”Youshould

alsoknowhowtorunthetests.However,beforedoingthis,makesurethatyouhaveallof

thesub-modulesinstalledintothesystem.Thesecanbeinstalledbyexecutingthe

followingcommand:

$gitsubmoduleupdate–init

Thetestscanberunbyexecutingthefollowingcommand:

$maketest

Thatishowthemodulecanbeused.

Chapter16-express-expose

Thisisusedforexposingtheobjects,functions,andrawjstotheclientside.Thisfeature

isgoodforsharingofsettings,utils,andthecurrentdatafortheuser.Thehelpersandthe

localvariablesarealsoexposedtotheclientside.

Toinstallthismodule,executethecommandgivenbelow:

npminstall-Sexpress-expose

Itcanbeusedasshownbelow:

varexpress=require(‘express’);

varexpose=require(‘express-expose’);

application=expose(application);

application.expose(…);

Theaboveishowthemodulecanbeusedinexpress4.x.Inexpress2.xand3.x,itcanbe

doneasfollows:

varexpress=require(‘express’);

varexpose=require(‘express-expose’);

application.expose(…);

Howtoexpresstheobjects

Onewaythatobjectscanbeexposedtotheclientsideisbyexposingtheproperties,and

mostprobablytheExpressconfiguration.Whenthe“app.expose(object)”isexposed,the

propertieswillbeexposedtothe“application.*”Theexamplegivenbelowshowshow

thiscanbedone:

application.set(‘views’,__dirname+‘/views’);

application.set(‘theviewengine‘,‘jade’);

application.set(‘title’,‘Sample‘);

application.set(‘defaultlanguage’,‘en’);

application.expose(application.settings);

Helpermethodscanalsobeexposedbyanotherusecase.Thiscanbeinthesamewaythat

youarecurrentlyexposing.Thisisshownbelow:

application.expose({en:‘English’,fr:‘French’},‘application’,‘languages’);

Youthenneedtooutputyourdefaultbuffertoyourtemplate.Forjadeusers,itcanbedone

asfollows:

script!=javascript

ForEJSusers,thiscanbedoneasfollows:

<script><%-javascript%></script>

RawJavaScriptstringscanalsobeexposedasshownbelow:

application.expose(‘varsome=“variable”;’);

ExposingFunctions

Anamedfunctioncaneasilybeexposed.Youonlyhavetopassitwithadefaultnamefor

thebuffertoreplaceitwithatemplatename.Anexampleofthisisshownbelow:

application.expose(functionsomeFunction(){

return‘yes’;

},‘foot’);

Thatishowitcanbedone.

Self-CallingFunctions

Ananonymousfunctioncanalsobepassed,andthiswillexecuteitselfsoastocreatea

wrapperfunction.Considertheexamplegivenbelow,whichshowshowthiscanbedone:

application.expose(function(){

functionnotify(){

alert(‘thiswillbeexecutedfinely:D’);

}

notify();

});

Thatishowitcanbedone.

Request-LevelExposure

Alltheabovewhichhasbeendiscussedcanbeappliedtotherequest-level.Considerthe

examplegivenbelowshowinghowtodothis.Hereistheexample:

application.get(‘/’,function(req,res){

varuser={name:‘john’};

res.expose(user,‘application.current.user’);

res.render(‘index’,{layout:false});

});

Chapter17-connect-render

Thisisahelperforthetemplaterenderinconnect.Itcanbeinstalledbyexecutingthe

followingcommand:

$npminstallconnect-render

Itcanbeusedasshownbelow:

varconnect=require(‘connect’);

varrender=require(‘connect-render’);

varapplication=connect(

render({

root:__dirname+‘/views’,

layout:‘layout.html’,

cache:true,//`false`forthedebug

helpers:{

sitename:‘connect-rendersamplesite’,

starttime:newDate().getTime(),

now:function(req,res){

returnnewDate();

}

}

})

);

application.use(function(req,res){

res.render(‘index.html’,{url:req.url});

});

application.listen(8080);

TheAPIcanbeusedasshownbelow:

/**

*connect-render:ATemplateRenderhelperfortheconnect

*

*Usecase:

*

*varrender=require(‘connect-render’);

*varconnect=require(‘connect’);

*

*connect(

*render({

*root:__dirname+‘/views’,

*cache:true,//mustbesetto`true`intheproductionenv

*layout:‘layout.html’,//orfalseifthereisnolayout

*open:“<%”,

*close:“%>”,//thedefaultejsclosetagis‘%>’

*helpers:{

*config:config,

*sitename:‘NodeBlogEngine’,

*_csrf:function(req,res){

*returnreq.session?req.session._csrf:””;

*},

*}

*});

*);

*

*res.render(‘index.html’,{title:‘IndexPage’,items:items});

*

*//nolayout

*res.render(‘blue.html’,{items:items,layout:false});

*

*@param{Object}[options={}]fortherenderoptions.

*-{String}layout,layoutname,thedefaultoneis`‘layout.html’`.

*Set`layout=”`or`layout=false`meaningthatnolayout.

*-{String}root,therootdirforviewfiles.

*-{Boolean}cache,thecacheviewcontent,thedefaultis`true`.

*Mustbeset`cache=true`onproduction.

*-{String}viewExt,theviewfileextname,thedefaultis`”`.

*@return{Function}renderingmiddlewareforthe`connect`

*/

functionmiddleware(options){}

Conclusion

ItcanbesaidthatExpressJSisaNodeframework.Itprovidesdeveloperswitha

frameworkwhichtheycanusetocreatewebandmobileapplications.Ithasnumerous

featureswhichdeveloperscantakeadvantageofsoastocreatetheirapplications.Itworks

byuseofitsmiddleware.Theframeworkalsoprovidesdeveloperswithnumerous

moduleswhichtheycanuseforthedevelopmentoftheirapplications.

Eachofthesemoduleshasitsowncommandwhichcanbeusedforitsinstallation.Touse

ofanyofitsmodules,youhavetobeginbyinstallingit.Itsupportstheuseofsessions

whichareveryusefulinthecreationofwebapplications.Ithasavarietyofoptionswhich

youcanuseforthepurposeofdevelopment.Youshouldlearnhowtousethedifferent

optionswhichareavailableforeachExpressJSmodule.Theserve-indexmoduleisused

forservingpageshavinglistingsofadirectorytoaparticularpath.

Thisisveryinterestingindevelopment.Withthe“cookie-sessions”module,onecan

provideguestsessionssothateachofthevisitorswillhaveasession,whether

authenticatedornot.ThisisalsooneofthebestandinterestingfeaturesinExpress.This

Nodeframeworkisveryeasytolearnevenforbeginners.Thisbookhelpsyouinlearning

howtouseit.