兼容IE8 input的placeholder的文字显示

if( !('placeholder' in document.createElement('input')) ){
    $('input[placeholder],textarea[placeholder]').each(function(){
        var that = $(this),
        text= that.attr('placeholder');
        // console.log(text);
        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('');
            }
        });
    });
}