Figure 5.6: DOM tree of parentNode example. firstChild

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Type
: Node
Description
: This property represents the first child of the node. If the node does not 
contain any children, then this property is set to null.
Comments
: This property is just a short cut for accessing the first item in a NodeList 
collection. In other words, myNode.firstChild and myNode.childNodes.item(0) represent 
the same node.
lastChild
Type
: Node
Description
: This property represents the last child of the node. If the node does not 
contain any children, then this property is set to null.
Comments
: This property is a short cut for accessing the last item in a NodeList 
collection. In other words, myNode.lastChild and myNode.childNodes.item( 
myNode.childNodes.length - 1 ) represent the same node.
Example
:










Both alerts from the above example produce element3. The first alert comes from using 
the lastChild property. The second alert finds the number of elements in the collection; 
subtracts 1 because the collection is indexed from 0, then goes to that item. Both 
methods go to the last child in the collection.
previousSibling
Type
: Node
Description
: This property represents a node that has a common parent and is the child 
of this parent that precedes the current node. If this child does not exist, then this 
property is set to null.
nextSibling
Type
: Node

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Description
: This property represents a node that has a common parent and is the child 
of this parent that follows the current node. If this child does not exist, then this property 
is set to null.
ownerDocument
Type
: Document node
Description
: This property represents the Document node of the DOM tree in which the 
current node resides.
Comments
: The Document node is the highest level parent for any node, and it always 
exists. The ownerDocument property is useful because it is a shortcut to the node that 
has special capabilities to create other nodes. A detailed description of the Document 
node is included in this chapter.
Node Methods
Most of the methods described in this section are used to manage and manipulate 
children of nodes. Not all nodes—for example, text nodes—are allowed to have child 
nodes. Since all the different node types are nodes, they inherit the following methods, 
even if the use of those methods doesn’t make sense. Using a method that would affect 
the children of a node that can’t have children results in an error. Please consult Figures 
4.13 through 4.19 for details concerning which nodes can have children and what kind of 
children are allowable.

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