XPath conditional text node selection

Question

I need to construct an xpath string to select all descendants of a certain table with these conditions:

• The table is a descendant of a form with a specific action attribute value.
• The selected descendants are text nodes.
• The text node content can only contain whitespace.

It'll probably look something like:

//form[@action = "submit.html"]//table//text()[ ...? ]

Any tips would be appreciated. Thanks.

Edit: Here is my previous working compromise:

function KillTextNodes(rootpath)
{
    XPathIterate(rootpath + '//text()', function(node)
    {
        var tagname = node.parentNode.tagName;
        if (tagname != 'OPTION' && tagname != 'TH')
            Kill(node);
    });
}

Here is my function based on the accepted answer:

function KillTextNodes(rootpath)
{
    XPathIterate(rootpath + '//text()[not(normalize-space())]', function(node) { Kill(node); });
}

To explain my motivation a little - I'm iterating through the DOM with Javascript, and run into the same problem that many others do where unexpected empty text nodes throw off the results. This function helps me out a lot by simply deleting all of the empty text nodes so that my iteration logic can stay simple.

Answer 1

Hi there. I need to construct an xpath string to select all descendants of a certain table with these conditions:

•The table is a descendant of a form with a specific action attribute value.

•The selected descendants are text nodes.

•The text node content can only contain whitespace.

Use :

//form[@action = "submit.html"]//table//text()[not(normalize-space())]

This selects all text nodes that have only white-space in them and that are descendents of any table that is a descendent of any form having an action attribute with value "submit.html".

Answer 2

Text nodes containing whitespace only will be stripped from the document representation - ie there won't actually be a node. That means you can't access the text itself, but what you can do is match a parent lacking a text node using not() - something like:

//form[@action = "submit.html"]//table//*[not(text())]

Though in your case I would guess that will be far more aggressive than you actually intend. As an aside, be careful with these // matches, they're not very efficient and again very aggressive.

(I've just noticed this isn't an XSLT question! If you're in JS land have you considered using DOM methods to get your list?)