In Lesson 31 you learned that there are a variety of ways to incorporate Ajax into a web application. The older technique of using hidden frames can still be found in many modern web applications, but the most popular way to add Ajax functionality to an application is by using the
XMLHttpRequest (XHR) object. Despite its name, you can retrieve more than XML with XHR. In fact, it's more commonly used to retrieve plain text.
There are essentially two types of browsers when it comes to XHR support. The first supports the native XHR object—meaning that XHR is built into the browser. The ...