XPathEvaluator: evaluate() method

The evaluate() method of the XPathEvaluator interface executes an XPath expression on the given node or document and returns an XPathResult.

Syntax

evaluate(expression, contextNode)
evaluate(expression, contextNode, resolver)
evaluate(expression, contextNode, resolver, type)
evaluate(expression, contextNode, resolver, type, result)

Parameters

expression: A string representing the XPath expression to be parsed and evaluated.
contextNode: A Node representing the context to use for evaluating the expression.
resolver Optional: A Node, null, or any object implementing the lookupNamespaceURI method. 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.

Examples

The following example shows the use of the evaluate() method.

HTML

html

<div>XPath example</div>
<div>Number of &lt;div&gt;s: <output></output></div>

JavaScript

const evaluator = new XPathEvaluator();
const result = evaluator.evaluate(
  "//div",
  document,
  null,
  XPathResult.ORDERED_NODE_SNAPSHOT_TYPE,
);
document.querySelector("output").textContent = result.snapshotLength;

Result

Specifications

Specification
DOM Standard # dom-xpathevaluatorbase-evaluate

Browser compatibility

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