Getting class name from div

I want to retrieve the class name of the last child element (class last div new3) in .find_class, but my code gives me class select3. How can I fix it?

Demo: http://jsfiddle.net/gBxan/5/

<div class="find_class mediumCell">
    <div class="new1 old1">
        <div class="select1"></div>
    </div>
    <div class="new2 old2">
        <div class="select2">开发者_StackOverflow中文版</div>
    </div>
    <div class="new3 old3"><!-- I want to get this div's class name 'new3' -->
        <div class="select3"></div>
    </div>
</div>

var find = $('div.find_class div:last').attr('class');
alert(find);

Use the child selector (>):

var find = $('div.find_class > div:last').attr('class');

Fiddle: http://jsfiddle.net/gBxan/6/
See also: MDN - CSS Selectors

$('.find_class').children(':last').attr('class');