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 &lt;div&gt;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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