//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);
 system.ipad = (navigator.userAgent.match(/iPad/i) != null) ? true : false;
 if (system.win || system.mac || system.xll || system.ipad) {
     alert("PC");
 } else {  
     var ua = navigator.userAgent.toLowerCase();  
     if(ua.match(/MicroMessenger/i)=="micromessenger") {  
         alert("微信浏览器");
     } else {  
         alert("手机");
     }  
 }