Introduction
1:
AJAX
and the Future Of Web Applications
2:
Client-Side Techniques with Smarter JavaScript
3:
Server-Side Techniques with PHP and MySQL
4: AJAX
Form Validation
5: AJAX Chat & JSON
6:
AJAX Suggest
and Autocomplete
7:
SVG (Scalable
Vector Graphics)
8: AJAX Grid
9: AJAX RSS
Reader
10: AJAX Drag and Drop
Appendix A:
Configuring Your Working Environment
Appendix B:
Using Smarter Tools to Write Better Code
Appendix C: Advanced XML
Index
Free Chapters:
Chapter 1:
AJAX and
the Future Of Web Applications [0.5 MB PDF]
Chapter 5:
AJAX Chat [1 MB PDF]
Free eBook:
AJAX Whiteboard mini-book
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Chapter 4: AJAX Form Validation
Validating input data is
an essential requirement for quality and secure software
applications. In the case of web applications, validation is an even
more sensitive area, because your application is widely reachable by
many users with varying skill sets and intentions. Validation is not
something to play with, because invalid data has the potential to
harm the application's functionality, and even corrupt the
application's most sensitive area: the database.
Input data validation means checking whether the data entered by the
user complies with previously defined rules, which are established
according to the business rules of your application. For example, if
you require dates to be entered in the YYYY-MM-DD format, then a
date of "February 28" would be considered invalid. E-mail addresses
and phone numbers are other examples of data that should be checked
against valid formats.
Carefully define the input data validation rules in the software
requirements document of the application you're developing, and then
use them consistently to validate your data! Historically, web form
validation was implemented mostly at the server-side, after the form
was submitted. In some cases, there was also some JavaScript code on
the client that performed simple validation such as checking whether
the e-mail address was valid, or if a user name had been entered.
The problems encountered with traditional web form validation
techniques are:
-
Server-side form
validation meets the limits of the HTTP protocol, which is a
stateless protocol. After submitting a page containing invalid
data an empty form reloads prompting the user to fill the form
all over again. To deal with this issue a special code needs to
be written.
-
When submitting
the page, the user needs to wait for a full page reload. For
every mistake that is done when filling the form, a new page
reload happens.
In this chapter, we will create a form-validation application
that implements the good old traditional techniques and adds an
AJAX flavor, thereby making the form more user-friendly and
responsive.
Even if you implement
AJAX validation, server-side validation is mandatory, because the
server is the last line of defense against invalid data. The
JavaScript code that gets to the client can not only be disabled
permanently from the browser's settings but also can be easily
modified or bypassed.
The code in this chapter can be verified online at
http://cristian.nexcess.net/ajax/validate
Chapter
4: AJAX Form Validation
- Implementing AJAX Form Validation
- Summary
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Paperback 250 pages
Released: February 2005
ISBN: 1847192825
ISBN 13:
978-1-904811-82-4
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