JQuery :: Get Value Of Custom Attribute From Parent

I have been learning jQuery and have been loving it so far. But can't figure out how to do the following...
1) Find the <a> inside a <ul> that has an active class.
2) Grab the value from the parent <li> and put it into a variable to be used elsewhere.

Here is the example markup...
<ul id="carousel">
<li class="carousel-item" carouselindex="1">
<a href="/someurl"><img src="/someimg" alt="" /></a>
</li>
<li class="carousel-item" carouselindex="2">
<a class="active" href="/someurl"><img src="/someimg" alt="" />
</a></li>
</ul>
So, in this example, I'd like to return a variable that = 2.