DOM @ XML

The XML Document Object Model (XML DOM) defines a standard way for accessing and manipulating XML documents.

The DOM presents an XML document as a tree-structure (a node tree), with the elements, attributes, and text defined as nodes.

Parsing the XML DOM

To manipulate an XML document, you need an XML parser. The parser loads the document into your computer's memory. Once the document is loaded, its data can be manipulated using the DOM. The DOM treats the XML document as a tree.

There are some differences between Microsoft's XML parser and the XML parser used in Mozilla browsers. In this tutorial we will show you how to create cross browser scripts that will work in both Internet Explorer and Mozilla browsers


Microsoft's XML Parser
Microsoft's XML parser is a COM component that comes with Internet Explorer 5 and higher. Once you have installed Internet Explorer, the parser is available to scripts.

Microsoft's XML parser supports all the necessary functions to traverse the node tree, access the nodes and their attribute values, insert and delete nodes, and convert the node tree back to XML.

To create an instance of Microsoft's XML parser, use the following code:

JavaScript:

var xmlDoc=new ActiveXObject("Microsoft.XMLDOM");

The first line of the script above creates an instance of the XML parser. The second line turns off asynchronized loading, to make sure that the parser will not continue execution of the script before the document is fully loaded. The third line tells the parser to load an XML document called "note.xml".

XML Parser in Mozilla, Firefox, and Opera
Mozilla's XML parser supports all the necessary functions to traverse the node tree, access the nodes and their attribute values, insert and delete nodes, and convert the node tree back to XML.

To create an instance of the XML parser in Mozilla browsers, use the following code:

JavaScript:

var xmlDoc=document.implementation.createDocument("ns","root",null);

The first parameter, ns, defines the namespace used for the XML document. The second parameter, root, is the XML root element in the XML file. The third parameter, null, is always null because it is not implemented yet

The following code fragment loads an existing XML document ("note.xml") into Mozillas' XML parser:

var xmlDoc=document.implementation.createDocument("","",null);
xmlDoc.load("note.xml");

The first line of the script above creates an instance of the XML parser. The second line tells the parser to load an XML document called "note.xml".