To learn more about the DOM, we recommend you check out the following resources:
??? http://www.quirksmode.org/dom/intro.html (a DOM tutorial)
??? http://www.javascriptkit.com/javatutors/dom.shtml (a DOM tutorial)
??? http://www.topxml.com/learning/games/b/default.asp (a useful and entertaining
DOM game)
??? http://krook.org/jsdom/ (a DOM reference)
XMLHttpRequest
XMLHttpRequest is the object you can use from your JavaScript code to make asynchronous
HTTP server requests. This allows you to initiate HTTP requests and receive responses from
the server in the background, without requiring the user to submit the page to the server.
Typically, when the response is received from the server, the DOM is used to alter the page
accordingly. This allows you to implement responsive functionality and visual effects backed
with live data from the server, without the user experiencing significant visual interruptions.
This is AJAX.
XMLHttpRequest was implemented by Microsoft in 1999 as an ActiveX object in Internet
Explorer, and it eventually became the de facto standard for all browsers, with it being supported
as a native object by all modern web browsers except Internet Explorer 6.
CHAPTER 13 ?– IMPLEMENTING AJAX FEATURES 401
Let??™s see how XMLHttpRequest works. You need to learn how to create the object, how to
initialize it by setting the appropriate parameters, how to start the server request, and how to
read the results.
Pages:
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514