Is there a built in method or defacto default plugin that will let you automatically assign an unique ID to an element in jQuery, or do you need to implement something like this yourself? I'm looking for the jQuery equivalent to Prototype's identify method

Here's an example. I have some HTML structure on a page that looks like this

<span id="prefix_1">foo bar</span>
...
<div id="foo">
   <span></span>
   <span></span>
   <span></span>
</div>

I want to assign each of the spans an ID that will be unique to the page. So after calling something like this

$('#foo span').identify('prefix');   //fake code, no such method

The rendered DOM would look something like this

<span id="prefix_1">foo bar</span>
...
<div id="foo">
   <span id="prefix_2"></span>
   <span id="prefix_3"></span>
   <span id="prefix_4"></span>
</div>

Is there anything official-ish/robust for jQuery, or is this something most jQuery developers roll on their own?