OSCON Learning Ajax

I’m currently in Alex Russell’s sold out Learning Ajax tutorial at OSCON. He’s generously made the latest version of the slides available online, as well as all of the demo code. Below are my notes from his excellent session. Since the slides are available online, I won’t go through my notes as thoroughly as I did for the Business for Geeks tutorial. Instead, I’ll simply highlight the items which Alex stressed in his talk:

  • Only use Ajax when it can make the users’ lives better! It may be fun to add gee-whiz effects to your web-app, but you must resist the temptation! Look at the bad name DHTML got from all of the websites which over-used it.
  • Whenever you run into trouble related to browser differences go to Quirks Mode first.
  • XMLHttp uses one of two available sockets, so if you have expensive jobs save them for last otherwise all of your little jobs will be blocked while two of the expensive jobs are working (or all of the little jobs will have to share a single queue if one socket is occupied with an expensive job).
  • Use synchronous XMLHttp requests sparingly — i.e. only when there are dependancies where you must download the required item, for example some JavaScript, before doing anything else.
  • Using innerHtml is fast and easy, but not very flexible. Try to use XML and the DOM to selectively interact with nodes (don’t forget that the server must declare it as “text/xml”!
  • Ajax style UIs should call the REST APIs your apps already expose (this is what flickr did)
  • What does “Grab the Chicken” mean? It’s used at JotSpot to discuss a neat feature the user discovers without being told about it. It comes from the Zelda Nintendo64 game where you’re trying to get over this wall and can’t figure it out, then you climb some nearby stairs and find a bunch of chickens — by grabbing one and then walking down the stairs you’re suddenly flying and can easily get over the wall.
  • Unfortunately, time ran out and Alex didn’t get to any of his application demos or “The Future” slides — which is a bummer because some of these things look really interesting.

TAGS: OSCON OSCON2005 Ajax XMLHttpRequest XMLHttp JavaScript XML DHTML