peepcode_unobtrusive_js.pdf

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Unobtrusive

Robust, Organized Javascripting

by Jarkko Laine

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Prototype.js

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PeepCode: Unobtrusive Prototype.js

Every effort was made to provide accurate infor-

mation in this document. However, neither Cody

Fauser nor Topfunky Corporation shall have any

liability for any errors in the code or descriptions

presented in this book.

“Rails” and “Ruby on Rails” are trademarks of

David Heinemeier Hansson.

This document is available for single users for

US$9 at PeepCode.com ( http://peepcode.com ).

Group discounts and site licenses can also be

purchased by sending email to peepcode@

topfunky.com.

thanks for buying this pre-release draft. may contain errors or odd formatting. final version will be available at soon.

contents

Introduction. Towards accessible Javascript

Brief history of Javascript on Rails

Introducing Low Pro

11 Event.addBehaviour

13 Behaviour classes

15 DOM builder

17 Refactoring an existing Rails application

26 Going DRY with multiple elements

34 Bubbling performance with event delegation

38 Caveats

40 More on Behaviour Classes

41 Writing your own behaviours

thanks for buying this pre-release draft. may contain errors or odd formatting. final version will be available at soon.

thanks for buying this pre-release draft. may contain errors or odd formatting. final version will be available at soon.

Introduction. Towards accessible Javascript

chapter 1

Let’s start by making a few terms straight. The three most important

terms in the scope of this book are accessibility, progressive enhance-

ment and unobtrusiveness. And while interconnected, they don’t

mean the same thing (at all).

The thing that’s been touted a lot lately in Javascript is unobtrusive-

ness. Many people talk about unobtrusive Javascript being all the

rage even though they actually mean accessible or using progressive

enhancement.

Accessibility in Javascript (and in web in general) means that as

many people as possible will have access to the content or function-

ality of the page even if the Javascript implementation in their brows-

ing device is lacking or nonexistent. Attaining some level of acces-

sibility is not only the right thing to do from the viewpoint of both the

bottom line and the readers/customers, but also required by law in

many countries. So writing accessible web applications even when

using the latest and greatest Javascript and Ajax whizbangs is the

learning target of this book.

Progressive enhancement , on the other hand, is a methodology for

building web pages and applications. Its roots are in the term grace-

ful degradation , which was dubbed to mean that web content using

Javascript and/or CSS would, well, degrade gracefully for users whose

browsers were incapable of taking advantage of these technologies.

The problem with graceful degradation is in its wording. It hints that

something is done afterwards to help these poor kids that can’t have

the cool toys to play with. This idea of making something afterwards

implicitly assumes that it will also cost extra. So when the function-

ality of your typical web app was ready and it was time to make it

degrade gracefully, time and money was short so the project lead

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