XML DOM Advanced
The XML DOM (Document Object Model) defines a standard way for accessing and
manipulating XML documents.
The XML DOM
The DOM views XML documents as a tree-structure. All
elements can be accessed through the DOM tree. Their content (text and
attributes) can be modified or
deleted, and new elements can be created. The elements, their
text, and their attributes are all known as nodes.
In an earlier chapter of this tutorial we introduced
the XML DOM , and used the XML DOM getElementsByTagName() method to retrieve
data from a DOM tree.
In this chapter we will describe some other commonly used XML DOM methods.
In the examples below, we have used the XML file:
books.xml.
To learn all about the XML DOM, please visit our XML DOM
tutorial.
Get the Value of an Element
The following code retrieves the text value of the first <title> element:
Example
x=xmlDoc.getElementsByTagName("title")[0].childNodes[0];
txt=x.nodeValue;
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Get the Value of an Attribute
The following code retrieves the text value of the "lang" attribute of the first
<title> element:
Example
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txt=xmlDoc.getElementsByTagName("title")[0].getAttribute("lang");
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Change the Value of an Element
The following code changes the text value of the first <title> element:
Example
x=xmlDoc.getElementsByTagName("title")[0].childNodes[0];
x.nodeValue="Easy Cooking";
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Change the Value of an Attribute
The setAttribute() method can be used to change the value of an existing attribute, or to create a new attribute.
The following code adds a new attribute called "edition" (with the value
"first") to each <book> element:
Example
x=xmlDoc.getElementsByTagName("book");
for(i=0;i<x.length;i++)
{
x[i].setAttribute("edition","first");
}
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Create an Element
The createElement() method creates a new element node. The createTextNode() method creates a new text node.
The appendChild() method adds a child node to a node (after the last child).
To create a new element with text content, it is necessary to create both an element node and a text node.
The following code creates an element (<edition>), and adds it to the
first <book> element:
Example
newel=xmlDoc.createElement("edition");
newtext=xmlDoc.createTextNode("First");
newel.appendChild(newtext);
x=xmlDoc.getElementsByTagName("book");
x[0].appendChild(newel);
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Example explained:
- Create an <edition> element
- Create a text node with value = "First"
- Append the text node to the <edition> element
- Append the <edition> element to the first <book> element
Remove an ElementThe removeChild() method removes a specified node (or element).
The following code fragment will remove the first node in the first <book> element:
Example
x=xmlDoc.getElementsByTagName("book")[0];
x.removeChild(x.childNodes[0]);
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Note: The result of the example above may be different depending on
what browser you use. Firefox treats new lines as empty text nodes, Internet
Explorer don't. You can read more about this and how to avoid it in the XML
DOM tutorial.
These were a few examples of things you can do with the XML DOM.
To learn all about the XML DOM, please visit our XML DOM
tutorial. <
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