placeholder兼容ie8

<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> 

来源：https://www.cnblogs.com/tzz-ing/p/5773841.html