jQuery: finding previous div

Question

<div class="a" style="display:none">Content 1</div>
<div class="a" style="display:none">Content 2</div>

some other HTML...

<span id="b">foobar</span>

How can I match the first div class="a" above the span id="b" to show() it? The id="b" is the only thing I know before.

Answer 1

Like this:

$('#b').prevAll('.a:first').show();

Answer 2

$("#b").closest(".a").show();

Try that.