Basic HTML version of Foils prepared 11 March 99

Foil 4 Cookies - "hidden" alternative

From Overview of JavaScript II -- From Cookies to Dynamical HTML CPS616 Technologies of the Information Age -- Spring Semester 99. by Geoffrey C. Fox (Tom Scavo)


1 Cookies were introduced by Netscape to preserve client side state
2 If you have a CGI script that services several clients (ordering T Shirts perhaps), it is neatest to use client and not server to store information such as name of user, passwords etc.
3 Traditionally saved state in forms for a session preserved using "hidden" fields
  • <INPUT type=hidden" name="username" value="" >
  • set by formname.username.value = WHATHAVEYOU;
4 Such hidden fields are passed to CGI scripts in same fashion as other variables set in form text fields
5 hidden values can either by set by JavaScript on client side or returned built into a page constructed by CGI script which might read N values and return a new form with M new fields for client to fill in and N old entries preserved in hidden fields
6 So hidden variables are nice but only preserved as long as you keep to page you started with or that returned by CGI script.

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Page produced by wwwfoil on Thu Mar 11 1999