让ie8支持 placeholder 属性

一、  ie8支持 placeholder 属性

 /*
  * ie8支持 placeholder 属性
  */
 $(function(){
 	 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('');
		        }
		      });
		    });
	  }
 })