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Does Ajax suck?
CS575 Spring 2007
Chanwit Suebsureekul
Web History
Static content
Dynamic content
Web application
Why Web Application?
Easy application deployment
Easy application distribution
No software to download
No installation
No update
Can be used from anywhere
Interactivity Issue
Simple request-response model
Not so responsive
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Send request, wait for response
Full page refresh
Ajax comes to rescue
What’s Ajax?
Asynchronous JavaScript and XML
A development technique for creating
interactive web applications
Makes web pages feel more responsive
Exchanges data with the server behind the
scenes
Partial page update
Ajax
A combination of technologies
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XHTML and CSS – page presentation
DOM – dynamic display and interaction
XML – data interchange and manipulation
XMLHttpRequest – asynchronous data retrieval
A JavaScript object
Send HTTP request
Parse XML response
Response can be handled asynchronously with a callback
function

JavaScript – binding everything together
Web Application Model
Ajax Examples
Ajax use:
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Instant save
Translating services
Smart shopping carts
Form validation (server side VS client side)
Etc.
Web application:
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Gmail
Google Maps
Google Docs & Spreadsheets
Etc.
Why Ajax Sucks (Most of the Time)
http://www.usabilityviews.com/ajaxsucks.html
The fundamental design of the Web is based on
having “the page” as the atomic unit of
information.
The page:
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the user’s view of the information on the screen
the unit of navigation
can be retrieved using the URL
Ajax breaks the concept of “the page”
Why Ajax Sucks (contd)
Breaks the BACK button
 The second-most used navigation feature
 Users can always get back to the firm ground

Breaking the BACK button is no less than a
usability catastrophe
Requires Ajax-compatible browsers
 W3C browser usage statistics
Print problems
Why Ajax Sucks (contd)
Authoring problems
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HTML is easy
Ajax is hard to learn that many page authors write
buggy code
Search problems
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Web spiders will only search for HREF, SRC, or some
link tags
They won’t follow Ajax JavaScript code
Related to the URL problem
Ajax Mistakes
Using Ajax for the sake of Ajax
Breaking the back button
Not giving immediate visual cues for clicking
widgets
Leaving offline people behind
Don’t make me wait for Ajax
Ajax Mistakes (contd)
Assuming AJAX development is single platform
development
Too much code makes the browser slow
Not having a plan for those who do not enable or
have JavaScript
Changing parts of the page unexpectedly
Ajax Mistakes (contd)
Not using links I can pass to friends or bookmark
Not cascading local changes to other parts of
the page
Scrolling the page and making me lose my place
Blocking Spidering
Why Ajax does NOT suck!
Web application VS Website
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Web application: a program made using web
technology
Website: a bunch of pages linked together
Ajax is intended and most useful for web
application, not website
Don’t blame the technology used but the person
who uses it
XMLHttpRequest Usability Guidelines
Do not load entire pages
Know the difference between a web application
and a website
Do not break what the user is focusing on
Consider how to handle users that cannot see
XMLHttpRequest
Do use it to eliminate confirmation pages
Do not over-use it