javascript

Chapter 10: The Document Object Model
The last method is removeAttribute() , which removes the attribute from the element altogether. This
does more than just clear the attribute ’ s value; it completely removes the attribute from the element as
shown here:
div.removeAttribute(“class”);
This method isn ’ t used very frequently, but it can be useful for specifying exactly which attributes to
include when serializing a DOM element.
IE versions 6 and earlier don ’ t support removeAttribute() .
The attributes Property
The Element type is the only DOM node type that uses the attributes property. The attributes
property contains a NamedNodeMap , which is a “ live ” collection similar to a NodeList . Every attribute
on an element is represented by an Attr node, each of which is stored in the NamedNodeMap object. A
NamedNodeMap object has the following methods:
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getNamedItem( name ) — Returns the node whose nodeName property is equal to name
removeNamedItem( name ) — Removes the node whose nodeName property is equal to name
from the list
setNamedItem( node ) — Adds the node to the list, indexing it by its nodeName property
item( pos ) — Returns the node in the numerical position pos
Each node in the attributes property is a node whose nodeName is the attribute name and whose
nodeValue is the attribute ’ s value. To retrieve the id attribute of an element, you can use the following code:
var id = element.attributes.getNamedItem(“id”).nodeValue;
Following is a shorthand notation for accessing attributes by name using bracket notation:
var id = element.attributes[“id”].nodeValue;
It ’ s possible to use this notation to set attribute values as well, retrieving the attribute node and then
setting the nodeValue to a new value, as this example shows:
element.attributes[“id”].nodeValue = “someOtherId”;
The removeNamedItem() method functions the same as the removeAttribute() method on the
element — it simply removes the attribute with the given name. The following example shows how the
sole difference is that removeNamedItem() returns the Attr node that represented the attribute:
var oldAttr = element.attributes.removeNamedItem(“id”);
The setNamedItem() is a rarely used method that allows you to add a new attribute to the element by
passing in an attribute node as shown in this example:
element.attributes.setNamedItem(newAttr);
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