Mozilla/5.0 (Linux; U; Android 2.3.6; zh-cn; GT-S5660 Build/GINGERBREAD) AppleWebKit/533.1 (KHTML, like Gecko) Version/4.0 Mobile Safari/533.1 MicroMessenger/4.5.255

function is_weixin(){
        var ua = navigator.userAgent.toLowerCase();
        if(ua.match(/MicroMessenger/i)=="micromessenger") {
            return true;
         } else {
            return false;
        }
    }

function isWechat() {
    const ua = navigator.userAgent.toLowerCase();
    return ua.match(/MicroMessenger/i)[0] === "micromessenger";
 }