问如何防止文本区域在键入和运行页面底部时跳舞？：JQuery/CSS

EN

<div>
 <div>
  <br><br> &nbsp;&nbsp;
    <textarea class="normal" name="myarea" id="myarea" style="height: 100px; overflow-y: hidden;"></textarea>
  </div>
</div> 
<input type="button" class="butt" value="ehehehhe" />

var myquery = {
  autoHeight: function(e) {
  $(e).css({
  'height': 'auto',
  'overflow-y': 'hidden'
 }).height(e.scrollHeight);
},
init: function() {
setTimeout(function() {
  $('textarea').each(function() {
    myquery.autoHeight(this);
  }).on('input', function() {
    myquery.autoHeight(this);
  });
}, 200);
$("textarea").keypress(function(e) {
   $(".butt").focus();    
   $(this).focus();    
});
  }

};

$(myquery.init);