Node
The DOM Node
interface is an abstract base
class upon which many other DOM API objects are based, thus letting those object types
to be used similarly and often interchangeably. As an abstract class, there is
no such thing as a plain Node
object. All objects that implement
Node
functionality are based on one of its subclasses. Most notable are
Document
, Element
, and DocumentFragment
.
In addition, every kind of DOM node is represented by an interface based on
Node
. These include Attr
, CharacterData
(which Text
, Comment
, CDATASection
and
ProcessingInstruction
are all based on), and DocumentType
.
In some cases, a particular feature of the base Node
interface may not
apply to one of its child interfaces; in that case, the inheriting node may
return null
or throw an exception, depending on circumstances. For example,
attempting to add children to a node type that cannot have children will throw an
exception.
Instance properties
In addition to the properties below, Node
inherits properties from its parent, EventTarget
.
Node.baseURI
Read only-
Returns a string representing the base URL of the document containing the
Node
. Node.childNodes
Read only-
Returns a live
NodeList
containing all the children of this node (including elements, text and comments).NodeList
being live means that if the children of theNode
change, theNodeList
object is automatically updated. Node.firstChild
Read only-
Returns a
Node
representing the first direct child node of the node, ornull
if the node has no child. Node.isConnected
Read only-
A boolean indicating whether or not the Node is connected (directly or indirectly) to the context object, e.g. the
Document
object in the case of the normal DOM, or theShadowRoot
in the case of a shadow DOM. Node.lastChild
Read only-
Returns a
Node
representing the last direct child node of the node, ornull
if the node has no child. Node.nextSibling
Read only-
Returns a
Node
representing the next node in the tree, ornull
if there isn't such node. Node.nodeName
Read only-
Returns a string containing the name of the
Node
. The structure of the name will differ with the node type. E.g. AnHTMLElement
will contain the name of the corresponding tag, like'audio'
for anHTMLAudioElement
, aText
node will have the'#text'
string, or aDocument
node will have the'#document'
string. Node.nodeType
Read only-
Returns an
unsigned short
representing the type of the node. Possible values are:Name Value ELEMENT_NODE
1
ATTRIBUTE_NODE
2
TEXT_NODE
3
CDATA_SECTION_NODE
4
PROCESSING_INSTRUCTION_NODE
7
COMMENT_NODE
8
DOCUMENT_NODE
9
DOCUMENT_TYPE_NODE
10
DOCUMENT_FRAGMENT_NODE
11
Node.nodeValue
-
Returns / Sets the value of the current node.
Node.ownerDocument
Read only-
Returns the
Document
that this node belongs to. If the node is itself a document, returnsnull
. Node.parentNode
Read only-
Returns a
Node
that is the parent of this node. If there is no such node, like if this node is the top of the tree or if doesn't participate in a tree, this property returnsnull
. Node.parentElement
Read only-
Returns an
Element
that is the parent of this node. If the node has no parent, or if that parent is not anElement
, this property returnsnull
. Node.previousSibling
Read only-
Returns a
Node
representing the previous node in the tree, ornull
if there isn't such node. Node.textContent
-
Returns / Sets the textual content of an element and all its descendants.
Instance methods
In addition to the methods below, Node
inherits methods from its parent, EventTarget
.
Node.appendChild()
-
Adds the specified
childNode
argument as the last child to the current node. If the argument referenced an existing node on the DOM tree, the node will be detached from its current position and attached at the new position. Node.cloneNode()
-
Clone a
Node
, and optionally, all of its contents. By default, it clones the content of the node. Node.compareDocumentPosition()
-
Compares the position of the current node against another node in any other document.
Node.contains()
-
Returns
true
orfalse
value indicating whether or not a node is a descendant of the calling node. Node.getRootNode()
-
Returns the context object's root which optionally includes the shadow root if it is available.
Node.hasChildNodes()
-
Returns a boolean value indicating whether or not the element has any child nodes.
Node.insertBefore()
-
Inserts a
Node
before the reference node as a child of a specified parent node. Node.isDefaultNamespace()
-
Accepts a namespace URI as an argument and returns a boolean value with a value of
true
if the namespace is the default namespace on the given node orfalse
if not. Node.isEqualNode()
-
Returns a boolean value which indicates whether or not two nodes are of the same type and all their defining data points match.
Node.isSameNode()
-
Returns a boolean value indicating whether or not the two nodes are the same (that is, they reference the same object).
Node.lookupPrefix()
-
Returns a string containing the prefix for a given namespace URI, if present, and
null
if not. When multiple prefixes are possible, the result is implementation-dependent. Node.lookupNamespaceURI()
-
Accepts a prefix and returns the namespace URI associated with it on the given node if found (and
null
if not). Supplyingnull
for the prefix will return the default namespace. Node.normalize()
-
Clean up all the text nodes under this element (merge adjacent, remove empty).
Node.removeChild()
-
Removes a child node from the current element, which must be a child of the current node.
Node.replaceChild()
-
Replaces one child
Node
of the current one with the second one given in parameter.
Examples
Remove all children nested within a node
This function remove each first child of an element, until there are none left.
js
function removeAllChildren(element) {
while (element.firstChild) {
element.removeChild(element.firstChild);
}
}
Using this function is a single call. Here we empty the body of the document:
js
removeAllChildren(document.body);
An alternative could be to set the textContent to the empty string: document.body.textContent = ""
.
Recurse through child nodes
The following function recursively calls a callback function for each node contained by a root node (including the root itself):
js
function eachNode(rootNode, callback) {
if (!callback) {
const nodes = [];
eachNode(rootNode, (node) => {
nodes.push(node);
});
return nodes;
}
if (callback(rootNode) === false) {
return false;
}
if (rootNode.hasChildNodes()) {
for (const node of rootNode.childNodes) {
if (eachNode(node, callback) === false) {
return;
}
}
}
}
The function recursively calls a function for each descendant node of
rootNode
(including the root itself).
If callback
is omitted, the function returns an
Array
instead, which contains rootNode
and all
nodes contained within.
If callback
is provided, and it returns
false
when called, the current recursion level is aborted, and the function
resumes execution at the last parent's level. This can be used to abort loops once a
node has been found (such as searching for a text node which contains a certain string).
The function has two parameters:
rootNode
-
The
Node
object whose descendants will be recursed through. callback
Optional-
An optional callback function that receives a
Node
as its only argument. If omitted,eachNode
returns anArray
of every node contained withinrootNode
(including the root itself).
The following demonstrates a real-world use of the eachNode()
function:
searching for text on a web-page.
We use a wrapper function named grep
to do the searching:
js
function grep(parentNode, pattern) {
let matches = [];
let endScan = false;
eachNode(parentNode, (node) => {
if (endScan) {
return false;
}
// Ignore anything which isn't a text node
if (node.nodeType !== Node.TEXT_NODE) {
return;
}
if (typeof pattern === "string" && node.textContent.includes(pattern)) {
matches.push(node);
} else if (pattern.test(node.textContent)) {
if (!pattern.global) {
endScan = true;
matches = node;
} else {
matches.push(node);
}
}
});
return matches;
}
Specifications
Specification |
---|
DOM Standard # interface-node |
Browser compatibility
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