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• 句法
• 范例
• 规范
• 浏览器兼容性
• 相关话题

evaluate() 方法在 XPathExpression interface executes an XPath expression on the given node or document and returns an XPathResult .

句法

XPathResult node.evaluate(contextNode, type, result);
					

参数

contextNode

节点 representing the context to use for evaluating the expression.

type 可选

Specifies the type of result to be returned by evaluating the expression. This must be one of the XPathResult.Constants .

result 可选

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.

返回值

XPathResult object representing the result of evaluating the XPath expression.

异常

INVALID_EXPRESSION_ERR

If the expression is not legal according to the rules of the XPathEvaluator ， XPathException 类型 INVALID_EXPRESSION_ERR 被引发。

TYPE_ERR

In case result cannot be converted to the specified type, an XPathException 类型 TYPE_ERR 被引发。

NAMESPACE_ERR

If the expression contains namespace prefixes which cannot be resolved by the specified XPathNSResolver ， DOMException 类型 NAMESPACE_ERROR 被引发。

WRONG_DOCUMENT_ERR

If the provided context node is from a document that is not supported by the XPathEvaluator ， DOMException 类型 WRONG_DOCUMENT_ERR 被引发。

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 ， DOMException 类型 NOT_SUPPORTED_ERR 被引发。

范例

The following example shows the use of the evaluate() 方法。

HTML

<div>XPath example</div>
<div>Number of <div>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;
					

结果

规范

规范	状态	注释
DOM (文档对象模型) 3 级 XPath 规范 The definition of 'XPathExpression.evaluate()' in that specification.	推荐	初始定义

浏览器兼容性

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No compatibility data found. Please contribute data for "api.XPathExpression.evaluate()" (depth: 1) to the MDN 兼容性数据存储库 .

元数据

• 最后修改： Mar 18, 2019

相关话题

1. XPathExpression
2. 方法

   1. evaluate()