Ajax: Intro notes

 Summary of Wikipedia page

from http://en.wikipedia.org/wiki/Ajax_(programming) :

Asynchronous Javascript And XML

except doesn't need XML: JSON often used instead
Also, doesn't have to be Asynchronous

Group of Web development techniques/technologies.

Javascript accesses DOM to allow user to dynamically interact with information displayed.

• Data exchanged asynchronously between browser and server via JavaScript and XMLHttpRequest object.
• Avoid full page reloads.

Technologies used:

• presentation uses [HTML or XHTML] + CSS
• Dynamic interactive data uses DOM
• Interchange of data via XML
• Manipulation of data vi XSLT
• Asynchronous communication via XMLHttpRequest object
• JavaScript to tie it all together

Drawbacks

• Dynamically updated web pages difficult to bookmark & save in history
• Web crawlers usually don't execute Javascript so need separate way to get into search engine indices.
• Asynchronous callback-style programming can be complex, hard to test & debug.