javascript 带有 dom 文档的 xpath
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xpath with dom document
提问by ertan
I'm trying the find a xml node with xpath query. but i cannot make it working. In firefox result is always "undefined" and chrome throws a error code.
我正在尝试使用 xpath 查询查找 xml 节点。但我不能让它工作。在 Firefox 中，结果总是“未定义”，chrome 会抛出错误代码。
<script type="text/javascript">
var xmlString = '<form><name>test</name></form>';
var doc = new DOMParser().parseFromString(xmlString,'text/xml');
var result = doc.evaluate('/form/name', doc,
null, XPathResult.ANY_TYPE, null);
alert(result.stringValue);
</script>
what's wrong with this code ?
这段代码有什么问题？
采纳答案by Topera
I don't know why did you get this error, but you can change XPathResult.ANY_TYPEto XPathResult.STRING_TYPEand will works (tested in firefox 3.6).
我不知道为什么会出现此错误，但是您可以更改XPathResult.ANY_TYPE为XPathResult.STRING_TYPE并且可以正常工作（在 Firefox 3.6 中测试）。
See:
看：
var xmlString = '<form><name>test</name></form>';
var doc = new DOMParser().parseFromString(xmlString,'text/xml');
var result = doc.evaluate('/form/name', doc, null, XPathResult.STRING_TYPE, null);
alert(result.stringValue); // returns 'test'
See in jsfiddle.
请参阅jsfiddle。
DETAILS:
细节：
The 4th parameter of method evaluateis a integer where you specify what kind of result do you need (reference). There are many types, as integer, string and any type. This method returns a XPathResult, that has many properties.
方法的第四个参数evaluate是一个整数，您可以在其中指定您需要什么样的结果（参考）。有很多类型，如整数、字符串和任何类型。此方法返回一个XPathResult，它具有许多属性。
You must match the property (numberValue, stringValue) with the property used in evaluate.
您必须将属性 (numberValue, stringValue) 与评估中使用的属性匹配。
I just don't understand why any typedidn't work with string value.
我只是不明白为什么any type不使用string value.
回答by Aurimas
XPathResult.ANY_TYPEwould return a node set for xpath expression /form/name, so result.stringValuewould have trouble converting node set to string. In this case you could use result.iterateNext().textContent
XPathResult.ANY_TYPE将为 xpath expression 返回一个节点集/form/name，因此result.stringValue将节点集转换为字符串时会遇到问题。在这种情况下，您可以使用result.iterateNext().textContent
However, an expression like count(/form/name)would return a number value when used with XPathResult.ANY_TYPEand you could use result.numberValueto retrieve the number in that case.
但是，count(/form/name)当使用 with 时，like 表达式将返回一个数字值，在这种情况下XPathResult.ANY_TYPE，您可以使用它result.numberValue来检索数字。
Some more detailed explanation at https://developer.mozilla.org/en/DOM/document.evaluate#Result_types
https://developer.mozilla.org/en/DOM/document.evaluate#Result_types 上的一些更详细的解释
