XML DOM Access Nodes

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XML DOM Tutorial
DOM HOME
DOM Introduction
DOM Nodes
DOM Node Tree
DOM Parsing
DOM Load Function
DOM Methods
DOM Accessing
DOM Node Info
DOM Node List
DOM Traversing
DOM Browsers
DOM Navigating
Manipulate Nodes
DOM Get Values
DOM Change Nodes
DOM Remove Nodes
DOM Replace Nodes
DOM Create Nodes
DOM Add Nodes
DOM Clone Nodes
DOM HttpRequest
XML DOM Reference
DOM Node Types
DOM Node
DOM NodeList
DOM NamedNodeMap
DOM Document
DOM DocumentImpl
DOM DocumentType
DOM ProcessingInstr
DOM Element
DOM Attribute
DOM Text
DOM CDATA
DOM Comment
DOM HttpRequest
DOM ParseError Obj
DOM Parser Errors
DOM Summary
Examples
DOM Examples
DOM Validator

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# XML DOM - Accessing Nodes

With the DOM, you can access every node in an XML document.

## Examples

The examples below use the XML file books.xml.
A function, loadXMLDoc(), in an external JavaScript is used to load the XML file.

Access a node using its index number in a node list
This example uses the getElementsByTagname() method to get the third <title> element in "books.xml"

Loop through nodes using the length property
This example uses the length property to loop through all <title> elements in "books.xml"

See the node type of an element
This example uses the nodeType property to get node type of the root element in "books.xml".

Loop through element nodes
This example uses the nodeType property to only process element nodes in "books.xml".

Loop through element nodes using node realtionships
This example uses the nodeType property and the nextSibling property to process element nodes in "books.xml".

## Accessing Nodes

You can access a node in three ways:

1. By using the getElementsByTagName() method

2. By looping through (traversing) the nodes tree.

3. By navigating the node tree, using the node relationships.

## The getElementsByTagName() Method

getElementsByTagName() returns all elements with a specified tag name.

### Syntax

    node.getElementsByTagName("tagname");

### Example

The following example returns all <title> elements under the x element:

    x.getElementsByTagName("title");

Note that the example above only returns <title> elements under the x node. To return all <title> elements in the XML document use:

    xmlDoc.getElementsByTagName("title");

where xmlDoc is the document itself (document node).

## DOM Node List

The getElementsByTagName() method returns a node list. A node list is an array of nodes.

The following code loads "books.xml" into xmlDoc using loadXMLDoc() and stores a list of <title> nodes (a node list) in the variable x:

    xmlDoc=loadXMLDoc("books.xml");

    x=xmlDoc.getElementsByTagName("title");

The <title> elements in x can be accessed by index number. To access the third <title> you can write:

    y=x[2];

Try it yourself.

Note: The index starts at 0.

You will learn more about node lists in a later chapter of this tutorial.

## DOM Node List Length

The length property defines the length of a node list (the number of nodes).

You can loop through a node list by using the length property:

    xmlDoc=loadXMLDoc("books.xml");

    x=xmlDoc.getElementsByTagName("title");

    for (i=0;i<x.length;i++)
      {
      document.write(x[i].childNodes[0].nodeValue);
      document.write("<br />");
      }

Example explained:

1. Load "books.xml" into xmlDoc using loadXMLDoc()
2. Get all <title> element nodes
3. For each title element, output the value of its text node

Try it yourself.

## Node Types

The documentElement property of the XML document is the root node.

The nodeName property of a node is the name of the node.

The nodeType property of a node is the type of the node.

You will learn more about the node properties in the next chapter of this tutorial.

Try it yourself.

## Traversing Nodes

The following code loops through the child nodes, that are also element nodes, of the root node:

    xmlDoc=loadXMLDoc("books.xml");

    x=xmlDoc.documentElement.childNodes;

    for (i=0;i<x.length;i++)
    {
      if (x[i].nodeType==1)
      {//Process only element nodes (type 1)
      document.write(x[i].nodeName);
      document.write("<br />");
      }
    }

Example explained:

1. Load "books.xml" into xmlDoc using loadXMLDoc()
2. Get the child nodes of the root element
3. For each child node, check the node type of the node. If the node type is "1" it is an element node
4. Output the name of the node if it is an element node

Try it yourself.

## Navigating Node Relationships

The following code navigates the node tree using the node relationships:

    xmlDoc=loadXMLDoc("books.xml");

    x=xmlDoc.getElementsByTagName("book")[0].childNodes;
    y=xmlDoc.getElementsByTagName("book")[0].firstChild;

    for (i=0;i<x.length;i++)
    {
    if (y.nodeType==1)
      {//Process only element nodes (type 1)
      document.write(y.nodeName + "<br />");
      }
    y=y.nextSibling;
    }

1. Load "books.xml" into xmlDoc using loadXMLDoc()
2. Get the child nodes of the first book element
3. Set the "y" variable to be the first child node of the first book element
4. For each child node (starting with the first child node "y"):
5. Check the node type. If the node type is "1" it is an element node
6. Output the name of the node if it is an element node
7. Set the "y" variable to be the next sibling node, and run through the loop again

Try it yourself.

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