Javascript XML and RSS

I am trying to create a website that can add items to an already created RSS xml document. The user would then input the already existing xml's URL, item's title, item's description and item's link. It would then spit out raw text (already existing xml document with appending information given) that I would manually copy into the RSS file on my website.

So, what I am wondering is if it is possible to do this in javascript and, if so, how push the raw text of the RSS xml document (specified at the URL input) to the body.

Thanks.