[jQuery] Return attribute content from XPath match //*[@id='banner']/@alt

[jQuery] Return attribute content from XPath match //*[@id='banner']/@alt


with something like..
<img id="banner" alt="This is a banner" />
//*[@id='banner']/@alt would return "This is a banner". Doing it this
way does not work, but is valid in XPather https://addons.mozilla.org/en-US/firefox/addon/1192
Is there another way to do this in JQuery (I am currently just looping
the return and extracting the attribute if set)?