↑
Main Page

Loading XML

using the string in position

and assigned it to the variable

oXmlDom

. If that version of the XML DOM

isn’t present on the user ’s machine, it causes an error, which is caught by the

try...catch

statement and

ignored. When that error occurs, the line

return oXmlDom

is completely skipped, and the

for

loop starts

again. Only if the XML DOM object is successfully created is it returned as the function value. If, on the

other hand, each version of the XML DOM is tested and no version is available, the function throws its

own error telling the user that MSXML isn’t installed on the system and processing cannot continue.

By using this function, you can be sure that the XML DOM version you are using is the most recent:

var oXmlDom = createXMLDOM();

Loading XML

Now that you have an XML DOM object, you load some XML into it. Microsoft’s XML DOM comes with

two methods for loading XML:

loadXML()

and

load()

The

loadXML()

method enables you to enter an XML string directly into the XML DOM:

oXmlDom.loadXML(“<root><child/></root>”);

The

load()

method is used to load an XML file from the server. Rather, the

load()

method can load an

XML file stored on the same server as the page that contains the JavaScript, meaning that you can’t load

XML from someone else’s server.

There are two modes of loading a file: synchronous and asynchronous. When you load a file in syn-

chronous mode, the JavaScript code waits for the file to be fully loaded before executing the next line of

code; a file loaded in asynchronous mode won’t wait, so you need to use an event handler to determine

when the file has been fully loaded.

By default, files are loaded asynchronously. To set files to load synchronously, just set the

async

prop-

erty to

false

oXmlDom.async = false;

You can then use the

load()

method by passing in the name of the file to load:

oXmlDom.load(“test.xml”);

After this line executes,

oXmlDom

contains a DOM Document representing the XML file, so you can use

all the DOM properties and methods:

alert(“Tag name of the root element is “ + oXmlDom.documentElement.tagName);

alert(“The root element has this many children: “ +

oXmlDom.documentElement.childNodes.length);

The code to create an XML DOM in Internet Explorer causes an error in any other

browser. Therefore, you must do a browser detect before attempting to create the

XML DOM in this way.

447

XML in JavaScript

18_579088 ch15.qxd 3/28/05 11:42 AM Page 447