title: JavaScript logger into a rolling file
body: <p>i've a JavaScript application.</p>
  
  <p>I'd like to use a logger but instead of logging to a console (like Firebug or Yahoo UI), I'd like to log to a file or several files.</p>
  
  <p>Ideally, It should be possible to back up the files when they reach a certain limit.</p>
  
  <p>thanks.</p>