区分ios和安卓，区分是否wx

// 区分安卓ios
var u = navigator.userAgent;
var isAndroid = u.indexOf('Android') > -1 || u.indexOf('Linux') > -1;
var isIOS = !!u.match(/\(i[^;]+;( U;)? CPU.+Mac OS X/);
// 区分是否微信
function is_weixin() {
   var ua = navigator.userAgent.toLowerCase();
   if (ua.match(/MicroMessenger/i) == "micromessenger") {
     return true;
   } else {
     return false;
   }
 }