Accelerated DOM Scripting with Ajax, APIs, and Libraries

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Jonathan Snook, Aaron Gustafson, Stuart Langridge, and Dan Webb

"Accelerated DOM Scripting with Ajax, APIs, and Libraries"

If your app uses a

to gather information, you??™ll probably want to try and validate that information to make sure
that what the user is filling in is reasonable in some way. Hence the convention that an * next
to a bit of a form means ???this part is mandatory; you must fill it in.??? It??™s equally important that
if you want the information you receive to be in a certain format you have your app enforce
that format. This is what validation is all about: having your app check what the user types to
confirm that it??™s what you were expecting. If you??™re asking users for the number of chickens
they own, it??™s a good idea to check that what they type in is a number instead of ???I don??™t own
any chickens,??? or something similar.
Validation helps with data quality. It also means that later bits of your programs can assume
that the data they have is valid; for example, if you want to sell the user another chicken, you can
write ???How would you like to own ($chickens + 1) chickens???? without having to worry about
what happens if you try to add 1 to what the user typed in. Validation is important.
Since this is a book about document object model (DOM) scripting, you might think that
you??™ll launch immediately into JavaScript, but that??™s not the case. One of the important points
about validation on the Web is that you must not just use JavaScript to do it. Users might have
JavaScript turned off; they might be using their cell phone; they might be demonstrating your
magnificent chickenbuyer.

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Schaum's Outline of Principles of Computer Science (page 230) Practical Reporting with Ruby and Rails (page 393) Foundation Flex for Designers (page 155)

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Jonathan Snook, Aaron Gustafson, Stuart Langridge, and Dan Webb

"Accelerated DOM Scripting with Ajax, APIs, and Libraries"