INT 213 - Prelims Handouts

8/8/2019 INT 213 - Prelims Handouts

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Internet 213Internet 213


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World Wide WebWorld Wide Web

Also called as WWW or W3Also called as WWW or W3

Allows users to use the InternetAllows users to use the Internet

easilyeasily

The web lets you connect by simplyThe web lets you connect by simply

clicking theclicking the hyperlinkhyperlink.. It applies a protocol calledIt applies a protocol called TCP/IPTCP/IP


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HyperlinkHyperlink

ThisThis isis aa word,word, phrasephrase

oror graphicgraphic imageimage thatthat

havehave URLsURLs (web(webaddress)address) hiddenhidden onon

themthem.. UsuallyUsually anan

underlinedunderlined wordword or or

phrasephrase..


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Transmission Control Protocol /Transmission Control Protocol /

Internet Protocol (TCP/IP)Internet Protocol (TCP/IP) The protocol of the InternetThe protocol of the Internet

Let the computers communicateLet the computers communicateNoteNote:: Internet Internet itself itself isis aa massivemassive

networknetwork of of hardwarehardware andand softwaresoftware

whilewhile WebWeb isis thethe applicationapplication facilitiesfacilities

providedprovided byby thethe InternetInternet


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Uniform Resource LocatorUniform Resource Locator

AA uniqueunique addressaddress forfor aa webweb

pagepage oror documentdocument ItIt consistsconsists ofof protocol protocol andand

domaindomain namename oror IPIP addressaddress andand

aa filefile namename


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http://www.yahoo.comhttp://www.yahoo.com

Protocol or

SchemeHost

Domain

Top-level

domain ortype of site


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HyperText Transfer ProtocolHyperText Transfer Protocol

ManagesManages thethe hypertexthypertext linkslinks thatthat areare

usedused toto navigatenavigate thethe WebWeb

YouYou cancan thinkthink ofof HTTPHTTP asas drivingdriving

thethe WebWeb

EnsuresEnsures thatthat browser browser correctlycorrectlyprocessprocess andand displaydisplay thethe variousvarious typestypes

ofof informationinformation containedcontained inin WebWeb

pagespages


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IP AddressIP Address

AnotherAnother wayway toto uniquelyuniquely identifyidentify

computerscomputers oror devicesdevices connectedconnected

toto thethe InternetInternet

UsingUsing aa seriesseries ofof fourfour groupsgroups ofof

numbersnumbers separatedseparated byby periodsperiods


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HyperText MarkupHyperText Markup

LanguageLanguage

The lingua franca of the Web.The lingua franca of the Web.

It is used to create web pages.It is used to create web pages.


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TagsTags

FormattingFormatting instructionsinstructions thatthat isis

usedused byby HTMLHTML documentsdocuments

ThatsThats whywhy itit isis calledcalled MarkupMarkup

because because ofof usingusing ofof tagstags inin

definingdefining elementselements ofof thethe WebWeb


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Parsing or RenderingParsing or Rendering

TheThe process process ofof assemblingassembling andand

formattingformatting anan HTMLHTML documentdocument ofof

aa webweb browserbrowser


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Briefhistory of JSBriefhistory of JS

JavaScriptJavaScript,, originallyoriginally nicknamednicknamed

LiveWireLiveWire andand thenthen LiveScriptLiveScript

whenwhen itit waswas createdcreated byby NetscapeNetscape,,

shouldshould inin factfact be be calledcalled

ECMAscriptECMAscript asas itit waswas renamedrenamedwhenwhen Netscape Netscape passed passed itit toto thethe

ECMAECMA forfor standardisationstandardisation..


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Role of JS on the WebRole of JS on the Web

BringsBrings HTMLHTML toto lifelife andand

makesmakes WebWeb pagespages dynamicdynamic..


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JavaScriptJavaScript

ItIt isis aa scriptingscripting languagelanguage (refers(refers toto

programmingprogramming languageslanguages thatthat areare

executedexecuted by by anan interpreterinterpreter fromfrom

withinwithin aa WebWeb browser)browser)


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F

ormats of JavaScriptF

ormats of JavaScript


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ClientClient--side JavaScriptside JavaScript

ProgramsPrograms areare passed passed toto thethe

computercomputer thatthat thethe browserbrowser isis on,on,

andand thatthat computercomputer runsruns themthem..


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ServerServer--Side JavaScriptSide JavaScript

TheThe alternativealternative isis serverserver side,side,

wherewhere thethe programprogram isis runrun onon thethe

serverserver andand onlyonly thethe resultsresults areare

passed passed toto thethe computercomputer thatthat thethe

browser browser isis onon.. ExamplesExamples ofof thisthiswouldwould bebe PHP,PHP, Perl,Perl, ASP,ASP, JSPJSP etcetc


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Logic and DebuggingLogic and Debugging


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BugBug

AnyAny errorerror inin aa program program thatthat

causescauses itit toto functionfunction incorrectly,incorrectly,

whetherwhether duedue toto incorrectincorrect syntaxsyntax oror

flawsflaws inin logiclogic


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DebuggingDebugging

DescribesDescribes thethe actact ofof tracingtracing andand

resolvingresolving errorserrors inin aa programprogram..

FirstFirst coinedcoined by by GraceGrace MurrayMurray

HopperHopper


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A FirstA First

JavaScriptJavaScriptProgramProgram


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The TagThe Tag

ItIt isis usedused toto notifynotify thethe WebWeb

BrowserBrowser thatthat thethe commandscommands thatthat

followfollow itit needneed toto bebe interpretedinterpreted byby

aa scriptingscripting engineengine..


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LanguageLanguage

AttributeAttribute ofof thethe tagtag tellstells

thethe browser browser whichwhich scriptingscripting

languagelanguage andand whichwhich versionversion ofof thethe

scriptingscripting languagelanguage isis beingbeing usedused..


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Note:Note:

IfIf youyou omitomit thethe LanguageLanguage attributeattribute

fromfrom thethe tag,tag, youryour

JavaScriptJavaScript programprogram shouldshould stillstill runrun..

However,However, thethe InternetInternet isis alwaysalways

changing,changing, itit isis difficultdifficult toto determinedetermine

whetherwhether competingcompeting scriptingscripting

languageslanguages suchsuch asas VBScriptVBScript willwill

becomebecome dominantdominant


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Creating a JavaScript ProgramCreating a JavaScript Program

11.. ToTo startstart aa JavaScriptJavaScript programprogram

useuse thethe tagtag

--

specifyingspecifying youryour browserbrowser thatthat youryour

usingusing JavaScriptJavaScript22.. CloseClose itit usingusing


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33.. UseUse thethe commentcomment tagtag toto telltell thethe

incompatibleincompatible browser browser toto ignoreignore

thethe codecode thatthat followsfollows..

>

44.. YouYou cancan embedembed JavaScriptJavaScript onon

headhead oror body body dependingdepending onon thetheapplicationapplication ofof youryour scriptscript


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My First JavaScript ProgramMy First JavaScript Program

Hello WorldHello World


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JavaScript is an OOPJavaScript is an OOP

ObjectObject--OrientedOriented ProgrammingProgramming

(OOP),(OOP), inin computercomputer science,science, typetype ofof

highhigh--levellevel computercomputer languagelanguage thatthatusesuses self self--contained,contained, modularmodular

instructioninstruction setssets forfor definingdefining andand

manipulatingmanipulating aspectsaspects ofof aa computercomputer

programprogram..


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ObjectObject

AA programming programming codecode andand datadata

thatthat cancan be be treatedtreated asas anan

individualindividual unitunit oror componentcomponent

ExEx.. DocumentDocument objectobject


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StatementsStatements

IndividualIndividual lineslines inin aa programmingprogramming

languagelanguage


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MethodsMethods

GroupGroup relatedrelated statementsstatements

associatedassociated withwith anan objectobject

ExEx.. write(write( )) andand writeln(writeln( ))


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Document ObjectDocument Object

RepresentsRepresents thethe contentcontent ofof aa

browsersbrowsers windowwindow

AnyAny text,text, graphics,graphics, oror otherother

informationinformation displayeddisplayed inin aa webweb

page page isis part part ofof thethe documentdocumentobjectobject


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ArgumentArgument

AnyAny typetype ofof informationinformation thatthat cancan

bebe passedpassed toto aa methodmethod

ExEx.. TheThe texttext stringstring withinwithin thethe

write()write() andand writelnwriteln methodsmethods ofof thethe

DocumentDocument objectobject


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Text or Literal StringText or Literal String

TextText thatthat isis containedcontained withinwithin

doubledouble quotationquotation marksmarks..

ExEx..

OutputOutput:: thisthis isis aa texttext stringstring


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Note:Note:

TheThe onlyonly differencedifference between between thethe

write()write() andand writeln()writeln() methodsmethods isis thatthat

thethe writelnwriteln methodmethod addsadds aa carriagecarriagereturnreturn afterafter thethe lineline ofof texttext..

HoweverHowever itit willwill bebe onlyonly recognizedrecognized ifif

itit isis withinwithin thethe HTMLHTML tagtag

pairpair..


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Tag Tag

ShortShort forfor PreformattedPreformatted TextText

TellsTells aa WebWeb browser browser thatthat anyany texttext

andand lineline breaks breaks containedcontained betweenbetweenopeningopening andand closingclosing tagtag areare toto bebe

renderedrendered exactlyexactly asas theythey appearappear

KnownKnown asas ContainerContainer ElementElement

because because itit containscontains texttext andand otherother

HTMLHTML tagstags


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JavaScript is Case SensitiveJavaScript is Case Sensitive

DocumentDocument..writewrite isis notnot similarsimilar toto

documentdocument..writewrite

UppercaseUppercase DD willwill notnot bebe recognizedrecognizedasas anan objectobject andand willwill causecause errorerror

YouYou mustmust useuse lowercaselowercase dd whenwhenreferringreferring toto documentdocument objectobject


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JavaScript VariablesJavaScript Variables ThenThen namename mustmust startstart withwith anan

alphabeticalphabetic (a(a--zz oror AA--Z)Z) charactercharacter oror

anan underscoreunderscore (_)(_)

TheThe restrest ofof thethe namename cancan containcontain anyany

letter,letter, anyany digit,digit, oror anan underscoreunderscore..

CantCant containcontain aa spacespace AvoidAvoid JavaScriptJavaScript reservedreserved wordswords asas

thethe namesnames ofof variablesvariables


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Debugging a ScriptDebugging a Script


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1. Capitalization1. Capitalization

JavaScriptJavaScript isis aa casecase sensitivesensitive

language,language, meaningmeaning thatthat itit treatstreats

capitalcapital andand lowercaselowercase versionsversions ofofthethe samesame letterletter asas differentdifferent

charactercharacter


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2. Spacing2. Spacing

SomeSome parts parts ofof aa scriptscript cancan

encounterencounter errorerror ifif incorrectincorrect

spacingspacing isis usedused..

TheThe best best wayway toto avoidavoid spacingspacing

errorerror isis toto paypay carefulcareful attentionattention totospacingspacing whilewhile youyou enterenter codecode


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3. Parenthesis( ), Brackets3. Parenthesis( ), Brackets

[ ], Braces{ }[ ], Braces{ } \\& Quotes & Quotes

JavaScriptJavaScript oftenoften usesuses fourfour typestypesofof symbolssymbols toto encloseenclose arguments,arguments,

valuesvalues oror numbersnumbers..


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4. Typographical Errors4. Typographical Errors

ErrorError inin enteringentering commandcommand suchsuch

asas zerozero ((00)) toto thethe letterletter (O)(O)..


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5. Others5. Others

JavaScriptJavaScript--compatiblecompatible browserbrowser

oftenoften displaydisplay aa JavaScriptJavaScript errorerror

windowwindow describesdescribes thethe typetype ofoferrorerror thethe browserbrowser encounteredencountered..


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AddingAdding

JavaScript to aJavaScript to aPagePage


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Body SectionBody Section

>


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Head SectionHead Section

>


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JavaScript Source FileJavaScript Source File

AA JavaScriptJavaScript codecode inin anan externalexternal

filefile

DesignatedDesignated withwith thethe filefile extensionextension

ofof jsjs andand containscontains onlyonly JavaScriptJavaScript

statementsstatements


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Reasons Behind .js Source FileReasons Behind .js Source File

YourYour HTMLHTML documentdocument willwill bebe neaterneater

TheThe JavaScriptJavaScript codecode cancan be be sharedshared

amongamong multiplemultiple HTMLHTML documentsdocuments JavaScriptJavaScript SourceSource FilesFiles hidehide

JavaScriptJavaScript codecode fromfrom incompatibleincompatible

browsersbrowsers

JavaScriptJavaScript sourcesource filesfiles helphelp hidehide youryour

JavaScriptJavaScript codecode


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Adding CommentsAdding CommentsTo a JavaScriptTo a JavaScript

ProgramProgram


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CommentComment

NonprintingNonprinting lineslines thatthat youyou placeplace

inin youryour codecode toto containcontain variousvarious

typestypes ofof remarks,remarks, includingincluding namenameofof thethe program,program, youryour namename andand

thethe datedate youyou createdcreated andand etcetc..,,


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Double Slash (//)Double Slash (//)

IndicatesIndicates aa singlesingle lineline

commentcomment.. EverythingEverything afterafter itit

onon thethe samesame lineline willwill bebe

ignoredignored byby thethe scriptscript engineengine..


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SlashSlash--Asterisk (/* & */)Asterisk (/* & */)

IndicatesIndicates aa block block commentcomment..

EverythingEverything afterafter itit willwill bebe

ignoredignored by by thethe scriptscript engineengine

untiluntil anan asteriskasterisk--slashslash isis

encounteredencountered..

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