CS 330 Class 6

1
CS 330 Class 6

• Programming plan for today
• Events.
• Forms with hidden fields.
• Form verification.

2
Events (15.1-15.2)

• Event an action an operating system recognizes
  and a corresponding event handler
• e.g. mouse button, incoming mail, a request to a
  server
• P. 285 has a good list of the available events.
• Our view is that event handlers are JavaScript
  code attached to attributes of HTML objects
• ltbody onLoad alert(hi there)gt
• ltinput type"button" value"Add "
  name"addButton"
• onClick"addNumbers(this.form)"gt
• Example focus.htm

3
Form with Hidden Fields

• Example guesthid.htm
• Allows user to select from different forms
• The hidden field tells the server which form is
  sending the message
• Response from frog.htm (mailed to me)
• whoAmIFrognameFreddytheFrogwarts100
• Can you think of any other use for a hidden field?

4
Form Verification (16.5)

• Forms have input elements with event handlers
  that respond to user interaction
• Event handlers are written in JavaScript
• Will look at this in more detail now
• Two approaches (guest3.htm)
• Verify each element as it is added via onChange
  event
• Verify the entire form as it is submitted to the
  server
• Next step (CGI) forms and their data are
  submitted to a server for processing