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NamedNodeMap

The

NamedNodeMap

object also has a

length

property to indicate the number of nodes it contains.

When used to represent attributes, each node in the

NamedNodeMap

is an

Attr

node, whose

nodeName

property is set to the attribute name. The

nodeValue

property is set to the attribute value. For example,

suppose you had this element:

<p style=”color: red” id=”p1”>Hello world!</p>

Also, suppose that the variable

that contains a reference to this element. You can access the value of

the

attribute like this:

var sId = oP.attributes.getNamedItem(“id”).nodeValue;

Of course, you could access this

attribute numerically, which is a little less intuitive:

var sId = oP.attributes.item(1).nodeValue;

You can change the

attribute by setting a new value to the

nodeValue

property:

oP.attributes.getNamedItem(“id”).nodeValue = “newId”;

Attr

nodes also have a

value

property that is exactly equal (and kept in sync with) the

nodeValue

property, as well as a

name

property that is kept in sync with

nodeName

. You use any of these properties

to modify or change the attributes.

Because this method is a little bit cumbersome, the DOM also defines three element methods to aid in

the assignment of attributes:

getAttribute(

name

)

— same as

attributes.getNamedItem(

name

).value

setAttribute(

name

newvalue

)

— same as

attributes.getNamedItem(

name

).value =

newvalue

removeAttribute(

name

)

— same as

attributes.removeNamedItem(

name

)

These methods are helpful in that they deal directly with the attribute values, completely hiding the

Attr

nodes. So, to retrieve the

attribute of the

<p />

used earlier, you can just do this:

var sId = oP.getAttribute(“id”);

And to change the ID, you can do this:

oP.setAttribute(“id”, “newId”);

As you can see, these methods are much less verbose than using the

NamedNodeMap

methods.

Keep in mind that each of these methods returns an

Attr

node, not the value of the

attribute.

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