A regex to identify spans with given class names

A regex to identify spans with given class names

I am in the process of writing a custom BBCode editor (I have excellent
reasons for doing this and not using a readymade effort) which generates,
amongst other things HTML markup such as
<span class='className'>...</span>
All of this is done and works well. However, I also need to do the reverse
transformation from HTML to my BBCode where from time-to-time I need to
identify all spans that use a given classname. For example
<span class='classNameA' style='font-family"Arial"'>Span content</span> so
I can convert it to my BBCode markup
[font=Arial]Span Content[/font]
I am well aware of the dangers of using regexs to parse any old HTML and
that is not my intent. I just need to reverse parse my own HTML tags -
with everything else passing through to the BBCode editor display.
To cut a long story short - I am no good with regexs particularly those
that require lookaheads etc. I would much appreciate any help with
creating a JavaScript regex for this job.