XPathEvaluator.createExpression() - Web APIs 编辑

This method compiles an XPathExpression which can then be used for (repeated) evaluations of the XPath expression.

Syntax

XPathExpression XPathEvaluator.createExpression(expression, resolver);

Parameters

expression

A DOMString representing the XPath expression to be created.

resolver Optional

Permits translation of all prefixes, including the xml namespace prefix, within the XPath expression into appropriate namespace URIs.

Return value

A XPathExpression representing the compiled form of 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.

NAMESPACE_ERR

If the expression contains namespace prefixes which cannot be resolved by the specified XPathNSResolver, a DOMException of type NAMESPACE_ERROR 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

Browser compatibility

BCD tables only load in the browser

See also

• Document.createExpression()
• XPathExpression