XPathEvaluator: evaluate() method

{{APIRef("DOM")}}

The evaluate() method of the {{domxref("XPathEvaluator")}} interface executes an XPath expression on the given node or document and returns an {{domxref("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 {{domxref("Node")}} representing the context to use for evaluating the expression.
• resolver {{optional_inline}}
  • : A {{domxref("Node")}}, null, or any object implementing the {{domxref("Node/lookupNamespaceURI", "lookupNamespaceURI")}} method. Permits translation of all prefixes, including the xml namespace prefix, within the XPath expression into appropriate namespace URIs.
• type {{optional_inline}}
  • : Specifies the type of result to be returned by evaluating the expression. This must be one of the {{domxref("XPathResult", "XPathResult", "Constants")}}.
• result {{optional_inline}}
  • : 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 {{domxref("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 {{domxref("XPathEvaluator")}}, a {{domxref("DOMException")}} of type INVALID_EXPRESSION_ERR is raised.

TYPE_ERR

In case result cannot be converted to the specified type, a {{domxref("DOMException")}} of type TYPE_ERR is raised.

NAMESPACE_ERR

If the expression contains namespace prefixes which cannot be resolved by the specified XPathNSResolver, a {{domxref("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 {{domxref("XPathEvaluator")}}, a {{domxref("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 {{domxref("XPathEvaluator")}}, a {{domxref("DOMException")}} of type NOT_SUPPORTED_ERR is raised.

Examples

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

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

Result

{{EmbedLiveSample('Examples')}}

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}