AJAX - The Complete Reference

240 Part II: Developing an Ajax Library^

var requestip = response.xhr.responseXML.getElementsByTagName("requestip")[0]

.firstChild.nodeValue;

var message = "Hello World to user from " + requestip + "!";

responseOutput.innerHTML = message;

}

else

responseOutput.innerHTML = "Cannot read packet: expected XML nodes not found";

Certainly for alternate formats like HTML, JSON, or even CSV, it is possible to come up

with a routine to look at the content to make sure it looks correct before using it. Figure 6-5

shows the Data Error Explorer (http://ajaxref.com/ch6/dataerror.html) being exercised,

which contains example code that exercises the ideas of this section.

FIGURE 6-5 Always check if a response is good data or bad data