Chapter 5 — Storing and Sharing Information 79

First, parse the supplied file into an XML object

my $doc = $parser->parsefile ($ARGV[0]) or die “Couldn’t parse $ARGV[0]”;

Extract a list of XML fragments enclosed by the tag

my $nodes = $doc->getElementsByTagName (“points”);

Get the number of objects returned

my $n = $nodes->getLength;

Now process through the list of tags and extract the data

for (my $i = 0; $i < $n; $i++)
{

Get a single tag structure from the XML document

my $node = $nodes->item ($i);

Extract the value from XXX

my $long = $node->getAttributeNode(“longitude”)->getValue();

Extract the value from XXX

my $lat = $node->getAttributeNode(“latitude”)->getValue();
print “Longitude: $long, Latitude: $lat\n”;
}

Free up the structure

$doc->dispose;

These are the key elements in the script:

1.The XML document is loaded and parsed into a DOM object.

2.A list of pointselements is extracted from the main document using the

getElementsByTagName()function.

3.A loop is used to iterate through the list of pointselements.

4.Each pointselement is extracted.

5.The values of the longitudeand latitudeattributes are obtained using the

getAttributeNode()function on the pointselement object.

Parsing XML with JavaScript

Once you go beyond the statically created Google Maps examples and start working with more
complicated sets of data, you must use XML as a method for exchanging information between
your web server application and the Google Maps client-side application. All of this is
achieved through JavaScript.

JavaScript, in its base form, is a fairly limited language designed with some strict rules and
goals in mind. Although it doesn’t contain a specific interface for working with XML docu-
ments, JavaScript can use the Document Object Model (DOM) to work with XML (and
HTML) documents. Technically, the DOM is not part of JavaScript, but JavaScript does