The evaluate()
method of the XPathEvaluator
interface executes an XPath expression on the given node or document and returns an XPathResult
.
Syntax
XPathResult XPathEvaluator.evaluate(expression, contextNode, resolver, type, result);
Parameters
- expression
- A
DOMString
representing the XPath expression to be parsed and evaluated. - contextNode
- A
Node
representing the context to use for evaluating the expression. - resolver Optional
- Permits translation of all prefixes, including the
xml
namespace prefix, within the XPath expression into appropriate namespace URIs. - 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 evaluator = new XPathEvaluator();
var result = evaluator.evaluate("//div", document, null, XPathResult.ORDERED_NODE_SNAPSHOT_TYPE);
document.querySelector("output").textContent = result.snapshotLength;
Result
Specifications
Specification | Status | Comment |
Document Object Model (DOM) Level 3 XPath SpecificationThe definition of 'XPathEvaluator.evaluate()' in that specification. | Recommendation | Initial definition |
Browser compatibility
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XPathEvaluator.evaluate() by Mozilla Contributors is licensed under CC-BY-SA 2.5.