ECA 225 Applied Interactive Programming1 ECA 225 Applied Online Programming cookies.

ECA 225 Applied Interactive Programming

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ECA 225

AppliedOnline

Programmingcookies


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cookies

cookies are small text files stored on the client’s computer

they can be used to store bits of information that can be used again and againuser’s namepassworddate of last visitpreferences


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serving cookies

cookies must be served up from a server, not simply loaded into a browser

Servers include: IISApacheXitamiPWS


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multiple cookie example

strInitialVisit3/13/2003 at 15:23.www.justustwo.com/ECA225/034709853442961766120982864029592910*userNameMichael Barathwww.justustwo.com/ECA225/034709853442961766120982864029592910*lastVisit10/7/2003 at 11:41.www.justustwo.com/ECA225/034709853442961766120982864029592910*compareLastVisitTue Oct 7 23:41:25 EDT 2003www.justustwo.com/ECA225/034709853442961766121042864029592910*visitCounter38www.justustwo.com/ECA225/034709853442961766121092864029592910*


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multiple cookie example cont …

previous example holds 5 cookies strInitialVisituserName lastVisitcompareLastVisitvisitCounter


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cookie parts

name / value pairmandatory

expiration date domain name path secure mode


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cookie parts cont …

userName Michael Barath www.justustwo.com/ECA225/ 073082316829570567294051024029546435*

name/value pair

domain & path

expiration date


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name / value pairmandatoryEG, userName = Michael

name of the cookie is userNamevalue associated with userName is ‘Michael’

all names and values must be strings


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expiration dateby default, cookies only last through the current

browser sessionwhen the browser is closed, the cookie perishes to create a cookie which persists, set the expires

attributeexpiration date can be any valid string date


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cookie parts cont … domain and path

a cookie always contains the address of the server that sent it

a cookie can only be read by the server which created it to begin with

by default, the browser sets the domain and path to the directory where the script resides – only scripts within that directory can access the cookie

to make the cookie accessible to all scripts on the server overwrite the default:

http://www.domain_name.com/


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secure tells the server whether or not a secure connection

is needed to access the cookie if the attribute is set, the cookie can only be sent

over a secure connection


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writing a cookie

a cookie is an object the cookie object is an attribute of the document

object refer to the cookie using dot notation

document.cookie


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writing a cookie cont …

to write a cookie holding the user’s nameget user input

variable userName holds value, eg, ‘Michael’write the cookie by assigning a properly formatted

string to document.cookie

var userName = prompt( ‘Please enter your name’, ‘ ‘ );


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the cookie after it is written

the syntax for writing the cookie

userNameMichael

document.cookie = “userName=” + userName;


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the previous example is a temporary cookie – it will perish as soon as the browser is closed

to set a cookie that persists, add an expiration date

to set a date object to 6 months in the future:

var exp = new Date( );exp.setMonth( exp.getMonth( ) + 6 );


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use the same document.cookie assignment to add an expiration date

separate the name/value pair from the expiration date with a ; ( semicolon )

after the semicolon, type the keyword expires assign the newly set expiration date to expires


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cookies can only contain strings convert the exp Date object to a string the

JavaScript method .toGMTString( ) concatenate, assign to document.cookie

document.cookie = “userName=” + username + “;expires=” + exp.toGMTString( );

string

string

variable

Date object converted to string


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cookie scriptif( document.cookie != "" ) {

userName = cookieVal( "userName" );} // end ifelse {userName = window.prompt( "Please enter your first

name", "" );setUserName();} // end else

function setUserName() {document.cookie = "userName=" + userName +

";expires=" + exp.toGMTString();} // end function


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cookie script cont … test to see if any cookies from this particular

server already exist

if cookies exist, this statement returns TRUE if no cookies exist, the else statement is executed

if( document.cookie != "" ) {

userName = cookieVal( "userName" );}


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cookie script cont …

the else statement calls a prompt box asking for the user’s name

a user-defined function named setUserName( ) is called to write the string to a cookie

else {userName = window.prompt(‘Please enter your first name’, ‘ ‘);setUserName( );}


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cookie script cont …

a cookie named userName is created, holding the value ‘Michael’, and expires in 6 months

a drawback to this example is the expiration date never changes

function setUserName() {

document.cookie = "userName=" + userName + ";expires=" + exp.toGMTString();

} // end of function


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reading cookies if the cookie already exists, we call cookieVal( )

to obtain the value associated with the cookie

in the function call we pass cookieVal( ) the name of the cookie (‘userName’) and assign the result to a variable of the same name




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reading cookies cont … function cookieVal( cookieName ) {thisCookie = document.cookie.split("; ");for( i = 0; i < thisCookie.length; i++ ) {

if( cookieName == thisCookie[i].split("=")[0] ) {return thisCookie[i].split("=")[1];} // end if

} // end forreturn 0;} // end function


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reading cookies cont … the split( ) method takes one argument, a string

delimiter the delimiter separates the cookie string into

distinct parts

split( ) returns an array of values, split where ever the delimiter occurs

thisCookie = document.cookie.split("; ");


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reading cookies cont … a cookie string which originally reads as

will now be an array named thisCookie which contains one element

( ‘userName=Michael)

thisCookie = ( ‘userName=Michael’ )


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reading cookies cont … multiple cookies, eg, ECA225 website

contains 5 cookies

each name=value pair is separated by a semicolon

strInitialVisituserNamelastVisitcompareLastVisitvisitCounter


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reading cookies cont …

creates the following array with 5 elements

thisCookie = (‘strInitialVisit=3/13/2003 at 15:23’, ‘userName=Michael’, ’lastVisit=10/7/2003 at 11:41’, ’compareLastVisit=Tue Oct 7 23:41:25 EDT 2003’, ‘visitCounter=38’ )

thisCookie = document.cookie.split("; ");


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reading cookies cont … run the array through a for loop which evaluates

each value of the thisCookie array

for( i = 0; i < thisCookie.length; i++ ) {if( cookieName == thisCookie[i].split("=")[0] ) {

return thisCookie[i].split("=")[1];} // end if

} // end for


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reading cookies cont … inside the for loop is another split( )method

which separates each value of the thisCookie array into a second array, split on the =

the new arrays look like this:

if( cookieName == thisCookie[i].split("=")[0] ) {

( ‘userName’ , ‘Michael’ )


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the if statement checks if the cookie name we passed into the function matches any of the array values at index 0, after the second split

if( cookieName == thisCookie[i].split("=")[0] ) {

( ‘userName’ , ‘Michael’ )

userName userName


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reading cookies cont … if it matches, the function returns the array value

at index 1, after the second split

if( cookieName == thisCookie[i].split("=")[0] ) {return thisCookie[i].split("=")[1];

userName userName

Michael


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if a value is returned, it is assigned to a variable in the initial if statement, which we can use in our script as we want




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updating expiration dateif( document.cookie != "" ) {

userName = cookieVal( "userName" );setUserName( );} // end if

else {userName = window.prompt( "Please enter your first

name", "" );setUserName();} // end else

function setUserName() {document.cookie = "userName=" + userName +

";expires=" + exp.toGMTString();} // end function

Date post:	15-Dec-2015
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