表格中上移下移置顶的js操作

<script>
$( function (){
 //上移
 var $up = $( ".up" )
 $up.click( function () {
  var $tr = $( this ).parents( "tr" );
  if ($tr.index() != 0) {
   $tr.fadeOut().fadeIn();
   $tr.prev().before($tr);
  }
 });
 //下移
 var $down = $( ".down" );
 var len = $down.length;
 $down.click( function () {
  var $tr = $( this ).parents( "tr" );
  if ($tr.index() != len - 1) {
   $tr.fadeOut().fadeIn();
   $tr.next().after($tr);
  }
 });
 //置顶
 var $top = $( ".top" );
 $top.click( function (){
  var $tr = $( this ).parents( "tr" );
  $tr.fadeOut().fadeIn();
  $( ".table" ).prepend($tr);
  $tr.css( "color" , "#f60" );
 });
});
</script>