javascript判断是否是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; 
    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="yz_pc_index.html"; 
    }else{ 
        window.location.href="yz_mobi_index.html"; 
    } 
</script>