Chapter 18. Using Ajax
Using Ajax not only substantially reduces the amount of data that must be sent back and forth, it also makes web pages seamlessly dynamic—allowing them to behave more like self-contained applications. The results are a much improved user interface and better responsiveness.
What Is Ajax?
The beginnings of Ajax as used today started with the release of
Internet Explorer 5 in 1999, which introduced a new ActiveX object,
XMLHttpRequest. ActiveX is Microsoft’s technology for signing plug-ins that install
additional software to your computer. Other browser developers later
followed suit, but rather than using ActiveX, they all implemented the
However, even before then, an early form of Ajax had already surfaced that used hidden frames on a page that interacted with the server in the background. Chat rooms were early adopters of this technology, using it to poll for and display new message posts without requiring page reloads.