title: What characters are valid for JavaScript variable names?
body: <p>Which characters can be used for naming a JavaScript variable?</p>
  
  <p>I want to create a small "extension library" for my non-JavaScript users here at work (who all seem to be squeamish when it comes to the language).  I love how jQuery and Prototype have both use the <code>$</code> dollar sign, and since I use jQuery, I'm looking for another nice single-character symbol to use.  </p>
  
  <p>I realize that I could just test out a number of characters, but I'm hoping to narrow down my list of characters to start with (in consideration of  future integration with another popular library, perhaps).</p>