让TextArea支持Table键

<SCRIPT LANGUAGE="JavaScript">
<!--
function testTab()
{
   var sel = document.selection.createRange();
   var mytext= sel.text;
   var i,j,k;
   if (event.shiftKey && event.keyCode == 9)
   {
      arr=mytext.split(String.fromCharCode(13,10))
      mytext=""

      for(k=0;k<arr.length;k++)
      {
         for (j=1; j<=4;j++)
         {
            if(arr[k].substr(0,1)=="\u0020")
            {
               arr[k]=arr[k].slice(1)
            }
         }
         mytext += arr[k] + ((k==(arr.length-1))? "" : String.fromCharCode(13,10));
      }
      with(sel){
         sel.text = mytext;
         collapse(true)
         moveEnd("character",0)
         moveStart("character",(mytext.length ) * -1)
         select()
      }

      window.event.cancelBubble = true;
      event.returnValue = false;
      return;
   }
   if (event.keyCode == 9)
   {
      arr=mytext.split(String.fromCharCode(13,10))
      mytext=""
      for(j=0;j<arr.length;j++)
      {
         mytext += "\u0020\u0020\u0020\u0020" + arr[j] + ((j==(arr.length-1))? "" : String.fromCharCode(13,10));
      }
      with(sel){
         sel.text = mytext;
         collapse(true)
         moveEnd("character",0)
         moveStart("character",(mytext.length -4) * -1)
         select()
      }

      window.event.cancelBubble = true;
      event.returnValue = false;
      return;
   }
}
//-->
</SCRIPT>