javascript如何判断是手机还是电脑访问本网页

 var system ={};  
    var p = navigator.platform;       
    system.win = p.indexOf("Win") == 0;  
    system.mac = p.indexOf("Mac") == 0;  
    system.x11 = (p == "X11") || (p.indexOf("Linux") == 0);     
    if(system.win||system.mac||system.xll){//如果是电脑跳转到百度  
        window.location.href="http://www.baidu.com/";  
    }else{  //如果是手机,跳转到谷歌
        window.location.href="http://www.google.cn/";  
    }