XPathExpression.evaluate()
The evaluate()
method of the
XPathExpression
interface executes an XPath expression on the given node or document and
returns an XPathResult
.
Syntax
XPathResult node.evaluate(contextNode, type, result);
Parameters
- contextNode
-
A
Node
representing the context to use for evaluating the expression. - type Optional
-
Specifies the type of result to be returned by evaluating the expression. This must be one of the
XPathResult.Constants
. - result Optional
-
Allows to specify a result object which may be reused and returned by this method. If this is specified as
null
or the implementation does not reuse the specified result, a new result object will be returned.
Return value
An XPathResult
object representing the result of evaluating the XPath
expression.
Exceptions
INVALID_EXPRESSION_ERR
If the expression is not legal according to the rules of the
XPathEvaluator
, an XPathException
of type
INVALID_EXPRESSION_ERR
is raised.
TYPE_ERR
In case result cannot be converted to the specified type, an
XPathException
of type TYPE_ERR
is raised.
NAMESPACE_ERR
If the expression contains namespace prefixes which cannot be resolved by the specified
XPathNSResolver
, a DOMException
of type
NAMESPACE_ERROR
is raised.
WRONG_DOCUMENT_ERR
If the provided context node is from a document that is not supported by the
XPathEvaluator
, a DOMException
of type
WRONG_DOCUMENT_ERR
is raised.
NOT_SUPPORTED_ERR
If the provided context node is not a type permitted as an XPath context node or the
request type is not permitted by the XPathEvaluator
, a
DOMException
of type NOT_SUPPORTED_ERR
is raised.
Example
The following example shows the use of the evaluate()
method.
HTML
<div>XPath example</div>
<div>Number of <div>s: <output></output></div>
JavaScript
var xpath = "//div";
var evaluator = new XPathEvaluator();
var expression = evaluator.createExpression("//div");
var result = expression.evaluate(document, XPathResult.ORDERED_NODE_SNAPSHOT_TYPE);
document.querySelector("output").textContent = result.snapshotLength;
Result
Specifications
Specification |
---|
DOM Standard # dom-xpathexpression-evaluate |
Browser compatibility
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