Re: select nodes with xpath, having by specific attribute named 'class' the 'subvalue part' set

Marek Mänd wrote:

> <style>
>   .marek{}
> </style>
> etc..
> <root>
> <element class="marek mand"/>
> <element class="mand marek"/>
> <element class="mand marekmänd"/>
> <element class="mand marekk"/>
> </root>
> 
> I would like to know what is the XPath expression for Mozillas 
> JavaScript document.evaluate method first argument, if i want to get all 
> the nodes, that have the 'css'-class named "marek" set.
> 
> By above data only 2 elements should be returned, because they and they 
> only have the 'css' class "marek" set. The XPath expression should not 
> match 'marekk' nor 'marekmänd'.

XPath 1.0 is not very strong in dealing with string values which are 
really a list of separate values thus if you are using XPath within 
JavaScript I think it is easier to start with XPath e.g.
   //element[contains(@class, 'marek')]
and then look at the result and use a JavaScript regular expression on 
the class attribute value to find those that match what you are looking for:

   function findElementsByClassName (xmlDocument, className) {
     var classNamePattern = new RegExp('(^|\\s+)' + className + '(\\s+|$)');
     var xpathExpression = '//*[contains(@class, "' + className + '")]';
     var elements = [];
     var xpathResult = xmlDocument.evaluate(
       xpathExpression,
       xmlDocument,
       null,
       XPathResult.ORDERED_NODE_ITERATOR_TYPE,
       null
     );
     var element;
     while ((element = xpathResult.iterateNext())) {
       classNamePattern.lastIndex = 0;
       if (classNamePattern.test(element.getAttribute('class'))) {
         elements.push(element);
       }
     }
     return elements;
   }

Using only XPath 1.0 it is very convoluted, watch out for line breaks 
the posting introduces:

   function findElementsByClassName (xmlDocument, className) {
     var xpathExpression =
'//element[normalize-space(@class) = "' + className + '"' +
' or starts-with(normalize-space(@class), "' + className + ' ")' +
' or contains(normalize-space(@class), " ' + className + ' ")' +
' or (substring(normalize-space(@class), 
string-length(normalize-space(@class)) ' +
' - string-length(" ' + className + '") + 1) = " ' + className + '")]';
     var elements = [];
     var xpathResult = xmlDocument.evaluate(
       xpathExpression,
       xmlDocument,
       null,
       XPathResult.ORDERED_NODE_ITERATOR_TYPE,
       null
     );
     var element;
     while ((element = xpathResult.iterateNext())) {
       elements.push(element);
     }
     return elements;
   }


-- 

	Martin Honnen
	http://JavaScript.FAQTs.com/