A website that I recently found very useful was the JS Fiddle website.
It basically sets up a test area for you to try out simple bits of code, saving you the time or creating a test area.
It also has the nice feature of being able to set up as different versions of HTML, and also include different versions of Jquery, saving you the time of setting up a head section of a page, uploading to a server, or inserting the include scripts for the javascript.
Well worth a try I think.