Cookies

1
Cookies
2
About Cookies

• Remember that you are storing data on the users
  computer
• Some users may prohibit cookies
• Cookies are
• Stored as a text string
• Text string contains name/value pairs
• Each name value pair is called a crumb
• Each name/value pair ends with a semicolon

3
Creating a Cookie

• The browser (document object) stores one cookie
  per page
• Its necessary to search the cookie for the
  desired data value
• The following statement creates a new cookie
• Document.cookie
• cookie1Data value

4
Relevant Name/Value Pairs (1)

• expiresdate
• Sets the expiration date of the cookie
• Standard is to used GMT format for the date
• If the expiration date is not set, then the
  cookie is deleted when the browser is closed
• If the expiration date is in the past, the cookie
  is deleted
• Future expiration dates cause the cookie to be
  deleted in that tag

5
Relevant Name/Value Pairs (2)

• pathpath
• Sets the cookies path
• Use to share information with other pages from
  the same domain
• Note that custom name/value pairs can be created
• One cookie string can store up to 20 name/value
  pairs

6
Creating a Cookie (Example)

• function setCookie()
• var cookieDate new Date() cookieDate.setTime(co
  okieDate.getTime()
• 24 60 60 1000)
• document.cookie "name1"
• document.FormCookie.CookieContent.value
  "expires" cookieDate.toUTCString()
  alert("cookie created "
• cookieDate.toUTCString()
• document.FormCookie.CookieContent.value)

7
Reading Cookies

• The process is less than sophisticated
• Need to use string functions to parse out the
  name/value pairs
• indexOf function gets the character position of a
  string
• length gets string length
• Use substring to extract the desired value

8
Reading a Cookie (Example part 1)

• First, see if the cookie exists by searching for
  the name
• var cookieData new String(document.cookie)
• var cookieHeader "name1"
• var cookieStart cookieData.indexOf(cookieHeader)
  cookieHeader.length
• cookieEnd cookieData.indexOf("",cookieStart)

9
Reading a Cookie (Example part 2)

• Check cookie exists and display it
• if (cookieData.indexOf(cookieHeader) ! -1)
• name cookieData.substring(
• cookieStart, cookieEnd)
• alert("Cookie lt" name "gt ")
• else
• alert("Cannot find cookie")

10
Deleting a Cookie

• The process is simple. Just reset the expiration
  time to a date in the past