Chapter 8 Working with XML Documents

Working with attributes

You can access the attributes of an element in the following ways:

DOMNode interface From the element node's attributes property.
Object interface From the getAttribute or getAttributeNode methods of the DOMElement object.

Using the DOMNode object to work with attributes

The following example writes out the names and values of the attributes of an element.

function displayAttributes( node ){               //1
  var i;                                          //2
  var attnode;                                    //3
  if( node.nodeType == 1){                        //4
    for( j=0; j < node.attributes.length; j++){   //5
      attnode = node.attributes.item(j)           //6
      document.writeln( attnode.nodeName );       //7
      document.writeln( attnode.firstChild.nodeValue  );
    }
  }
}

If the supplied element has a start tag of this form:

<Region Type="Province">

Then the output is:

Type
Province

In this example, the attribute node has a child that is a text object. The nodeValue of this text object can also be used to retrieve the attribute value.

Attribute nodes

Attributes do not occupy a place in the document tree. A DOMNode object that represents an attribute has no parents and no siblings. Any attempt to access these properties returns null.
You can access an attribute node of an XML element using the attributes property of the element node. This property returns a DOMNamedNodeMap object. You can access the individual attributes either by index (as in the sample code above) or by name. The following statement sets attnode to the Type attribute of the element:
```
attnode = node.attributes.getNamedItem( "Type" );
```

Using the DOMAttribute object to work with attributes

The DOMAttribute object corresponds to an attribute of an XML element. The DOMAttribute object inherits all the properties and methods from the DOMNode object. In addition, it supports some properties and methods specific to attributes.

You can access the attributes of an element in the following ways:

Get the value of an attribute with a given name The following sample code takes a list of elements as input (elemList ), and lists the value of all the Type attributes:
```
for( i = 0 ; i < elemList.length ; i ++ ){
  elem = elemList.item(i);
  document.writeln( elem.getAttribute( "Type" ) );
}
```

Get the DOMAttribute object for an attribute The following sample code lists the value of each Type attribute for a list of elements:

for( i = 0 ; i < elemList.length ; i ++ ){
  elem = elemList.item(i);
  att = elem.getAttributeNode( "Type" );
  document.writeln( att.name + " = " + att.value );
}

The DOMAttribute object also has methods and properties that you can use to alter XML documents. For more information, see "Using the DOM interface to create and edit XML documents".