selected option for select box while button click

selected option for select box while button click

What is wrong with below code: any idea
HTML :
  1. <select class="widthed" name="moveattrribseq" id="moveattrribseq" multiple="multiple" size="10" >
  2.                 <!-- Options will be added dynamically -->
  3.               </select>
  4.  
  5. <input type="button" class ="buttontext" name="next" id="next" value="Next">


Jquery :
  1. $(document).ready(function() {
  2.       $('#next').click(function() {
  3.         $('select#moveattrribseq').attr('selected','selected');      // this line is not working...

  4.       });
  5. });

I need to auto select all select box options when I click button.