jquery input placeholder支持兼容ie7，ie8

<input type="text" placeholder="搜索产品名称"/><input type="password" placeholder="密码"/>

/* * jQuery placeholder, fix for IE6,7,8,9 * @author byh */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');            var holder = $('<span></span>').text(txt).css({position:'absolute', left:pos.left, top:pos.top, height:h, lienHeight:h, paddingLeft:paddingleft, 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jQuery(function(){    JPlaceHolder.init();    });