用JavaScript解决Placeholder的IE8兼容问题

<script type="text/javascript">   
  if( !('placeholder' in document.createElement('input')) ){   
  
    $('input[placeholder],textarea[placeholder]').each(function(){    
      var that = $(this),    
      text= that.attr('placeholder');    
      if(that.val()===""){    
        that.val(text).addClass('placeholder');    
      }    
      that.focus(function(){    
        if(that.val()===text){    
          that.val("").removeClass('placeholder');    
        }    
      })    
      .blur(function(){    
        if(that.val()===""){    
          that.val(text).addClass('placeholder');    
        }    
      })    
      .closest('form').submit(function(){    
        if(that.val() === text){    
          that.val('');    
        }    
      });    
    });    
  }   
</script>  

　　非常棒