js判断手机端还是pc端

 <script type="text/javascript">

    <!--
    //平台、设备和操作系统
    var system ={
        win : false,
        mac : false,
        xll : false
    };
    //检测平台
    var p = navigator.platform;
    alert(p);
    system.win = p.indexOf("Win") == 0;
    system.mac = p.indexOf("Mac") == 0;
    system.x11 = (p == "X11") || (p.indexOf("Linux") == 0);
    //跳转语句
    if(system.win||system.mac||system.xll){//转向后台登陆页面
        window.location.href="login.jsp";
    }else{
        window.location.href="wapLojin.jsp";
    }
    -->
</script>