• Accessibility
• Optimization
  • On the wire
  • In the browser
• Cross-Domain Ajax

• It's possible to make accessible Ajax UI's
• It's not easy
• But it's getting easier

• Focus
• Feedback
• "What Is It?"

• Large-text modes
• High-contrast mode
• "Large-target" modes
• Colorblindness
• Other Section 508

• Clean HTML helps
• WAI role and state information
• Tabindex for keyboard navigation
• Poor communication with assistive technologies
• Assistive software still lags
• W3C WCAG isn't helping anything

• Defines richer set of what something "is"
• Must live in XHTML 2 namespace
• As a result, needs to be set at runtime
• Calling focus() almost well supported
• Setting up keyboard accellerators is difficult
• We're working on generalized a11y solutions in Dojo

Ajax Accessibility Is Hindered By Lack Of A Coherent Shadow DOM

Optimization

• Bandwidth
• Latency
• Parallel or Serial?

• TamperData
• Ethereal
• Server logs

• Cache
• Make it smaller
• Request fewer resources
• Parallelize
• Delay loading
• Host closer to endpoint

• Client side
  • Expect 50% cache miss rates at scale
  • Last-Modified, Cache-Control, ETags, If-Modified-Since
  • IE is fickle!
  • Cal Henderson's "Serving JavaScript Fast" article
• Server side
  • Squid
  • memcached
  • mod_cache and physical partitions
  • Database tuning

• gzip encoding (mod_deflate)
• White space and comment removal (then cache!)
• Dead code stripping

• Concat smaller JS into larger "common" files
• CSS background image "trick"
• Exotic MIME games

• JS files are loaded serially
• 2 connections per domain!
• Host static resource "off domain"
• Sub-domains count
• CDN's help

• Load code in response to user actions
• Requires careful development practices
• Or a package system
• Dojo provides such a system

• CDN's
• Exotic form of caching
• AOL hosts Dojo in their CDN for all to use

• Tools much less mature
• Venkman profiler
• Lots of ad-hoc speed comparisons
• Hard-won experience with various rendering engines

• innerHTML fast vs. DOM
• JS iteration is slow
• JS regular expressions are slow
• JS function calls are fast
• IE GC "wall"
• "First visit" hit

• "Closures cause memory leakage"
• "DOM iteration is slow"
• "External style sheets are faster"
• "Objects are cheap"
• "Array joins are faster than string addition"

• Your first guess will be wrong
• Starting from the top and work down to slow components
• Always keep a log
• Know when to stop
• Always verify your cache settings
• If it's not what your clients are using, it's not what your clients are using
• Leakage !== Peak Memory Usage Increases

• Local data is interesting
• But it'll always be more interesting when given more context
• Mashups already do this, but protocol is opaque
• Better understanding of techniques will drive adoption

• Pioneered by James Burke of AOL (a Dojo contributor)
• Requires explicit cooperation of 3rd-party domain
• Can return HTML document content
• Few worries about malicious content or cookie leakage
• May be slow in some circumstances

• Proposal from Bob Ippolito
• Requires explicit cooperation of server
• Very fast, can return content of arbitrary type and size
• Variant already in use by Yahoo
• Potentially unsafe, executes remote code in page context

X-Z of Y results

• http://flickr.com/photo_zoom.gne?id=184612846&size=o
• http://flickr.com/photos/myradphotos/3111332/