让IE支持placeholder属性

       var JPlaceHolder = {
            //检测
            _check: function ()
            {
                return 'placeholder' in document.createElement('input');
            },
            //初始化
            init: function ()
            {
                if (!this._check())
                {
                    this.fix();
                }
            },
            //修复
            fix: function ()
            {
                jQuery(':input[placeholder]').each(function (index, element)
                {
                    var self = $(this), txt = self.attr('placeholder');
                    self.wrap($('<div></div>').css({ position: 'relative', zoom: '1', border: 'none', background: 'none', padding: 'none', margin: 'none' }));
                    var pos = self.position(), h = self.outerHeight(true), paddingleft = self.css('padding-left'), paddingtop = self.css('padding-top'), paddingbottom = self.css('padding-bottom');
                    var holder = $('<span></span>').text(txt).css({ position: 'absolute', left: pos.left, top: pos.top, height: h, lienHeight: h, paddingLeft: paddingleft, paddingTop: paddingtop, paddingBottom: paddingbottom, color: '#aaa' }).appendTo(self.parent());
                    self.focusin(function (e)
                    {
                        holder.hide();
                    }).focusout(function (e)
                    {
                        if (!self.val())
                        {
                            holder.show();
                        }
                    });
                    holder.click(function (e)
                    {
                        holder.hide();
                        self.focus();
                    });
                });
            }
        };
        //执行
        $(function ()
        {
            JPlaceHolder.init();
        });