XML DOM Node List

The XML DOM uses a tree-structure, also known as a node-tree, to view an XML document, i.e., each node can be accessed through the tree. We can also modify, delete, or create a new element through the tree. The getElementsByTagName() method and the childNodes property returns a list of nodes.

DOM Node List:

The childNodes or getElementsByTagName() properties or methods is used to return a node list object. A list of nodes is represented by the node list object in the same order as in the XML. The index numbers starting from 0 are used to access the nodes in a node list.

Books.xml:

  
    
    Author Name
    2020
    100.00
  

  
    
    Author 1
    Author 2
    Author 3
    Author 4
    2004
    350.00
  

Example: To return a node list of title elements in “books.xml” which is loaded into the variable xmlDoc:

x = xmlDoc.getElementsByTagName("title");

Explanation:

Here, x becomes a node list object, after the execution of the above code.

Example: To return the text from the first <title> element in the node list (x):

Output:

Explanation:

In the above example, the value of the “txt” variable becomes “ABC”, after the execution of the above code.

Node List Length:

By keeping itself up-to-date, a node list object automatically updates the list, if an element is deleted or added. The number of nodes in a list represents the length property of a node list. For looping through each element in a list, the length of the node list can be used.

Example: To return the number of <title> elements in “books.xml”:

x = xmlDoc.getElementsByTagName('title').length;

Explanation:

Here, the value of x will be 2, after the execution of the above code.

Example: Using the length property to loop through the list of <title> elements:

Output:

Explanation:

In the above example, we are loading the “books.xml” into xmlDoc. To hold a node list of all title elements, we will set the x variable. The text node values can be collected from the <title> elements.

DOM Attribute List (Named Node Map):

To get a list of the attribute nodes, the attributes property of the element node is used, also called a named node map. It is similar to a node list. However, there are some differences in methods and properties. By keeping itself up-to-date, an attribute list automatically updates the list, if an attribute is deleted or added.

Example: To get a list of attribute nodes from the first <book> element in “books.xml”:

x = xmlDoc.getElementsByTagName('book')[0].attributes;

Explanation:

In the above example, x.length represents the number of attributes, after the execution of the code. Also, to return an attribute node, the x.getNamedItem() can be used.

Example: To get the value of the “category” attribute, and the number of attributes of a book:

Output:

Child
1

Explanation:

In the above example, the “books.xml” is loaded into xmlDoc. Now, to hold a list of all attributes of the first <book> element, we will set the x variable. The value of the “category” attribute and the length of the attribute list can then be retrieved.