A small YUI3 module which modifies Node's focus() function to take position argument "end" or number of characters and places cursor there.
  <script type="text/javascript" src="http://yui.yahooapis.com/3.5.1/build/yui/yui-min.js"></script>
  <script type="text/javascript" src="focusPosition.js"></script>
  <script type="text/javascript">
    YUI ().use ("focusPosition", function (Y) {
      Y.one("textarea").focus ("end");
    });
  </script>