Xpath select n-th node

Question

I have a XML like this

<div class="yay">
 <div class="foo"></div> 
 <div class="foo"></div>
 <div class="bar"></div>
 <div class="foo"></div>
 <div class="bar"></div>
 <div class="foo"></div>
</div>

Is there a way to select the n-nth div where class is "foo"?

I'd select all foos with //div[@class="yay"/div[@class="foo"]

If I want to select foo #3 how do I do that? Something like:

//div[@class="yay"/div[@class="foo"][3] ?

Answer 1

This is one of the most FAQ in XPath.

Use:

(//div[@class="yay"]/div[@class="foo"])[3]

Explanation:

The XPath pseudo-operator // has lower precedence (priority) that the [] operator.

Thus

//div[@class="yay"]/div[@class="foo"][3]

means:

Select every div whose class attribute has the value "foo" and that (the div) is the third such div child of its parent.

If there are more than one parent div elements that have three or more such children, then all of the 3rd children are selected.

As with many expression languages, the way to override built-in priority is to use parenthesis.