要区分用户是通过"微信内置浏览器"还是"原生浏览器"打开的WebApp, 可以通过navigator.userAgent来进行判断.
以下是对各种平台上微信内置浏览器和原生浏览器UA的对比
PC版微信:
Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/39.0.2171.95 Safari/537.36 MicroMessenger/6.5.2.501 NetType/WIFI WindowsWechat
PC Chrome:
Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/49.0.2623.110 Safari/537.36
iPhone版微信:
Mozilla/5.0 (iPhone; CPU iPhone OS 9_3 like Mac OS X) AppleWebKit/601.1.46 (KHTML, like Gecko) Mobile/13E233 MicroMessenger/6.3.15 NetType/WIFI Language/zh_CN
iPhone Safari:
Mozilla/5.0 (iPhone; CPU iPhone OS 9_3 like Mac OS X) AppleWebKit/601.1.46 (KHTML, like Gecko) Version/9.0 Mobile/13E233 Safari/601.1
Android版微信:
Mozilla/5.0 (Linux; Android 5.0.1; GT-I9502 Build/LRX22C; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/43.0.2357.121 Mobile Safari/537.36 MicroMessenger/6.1.0.78_r1129455.543 NetType/WIFI
Android (Samsung S4) 默认浏览器:
Mozilla/5.0 (Linux; Android 5.0.1; SAMSUNG GT-I9502 Build/LRX22C) AppleWebKit/537.36 (KHTML, like Gecko) SamsungBrowser/2.1 Chrome/34.0.1847.76 Mobile Safari/537.36
注: Mi4刷的WinPhone系统...
WinPhone版微信:
Mozilla/5.0 (Windows Phone 8.1; ARM; Trident/8.0; Touch; rv:11.0; WebBrowser/8.1; IEMobile/11.0; XIAOMITEST; MI4) like Gecko false
WinPhone 默认浏览器:
Mozilla.5.0 (Windows Phone 10.0; Android 4.2.1; XIAOMITEST; MI4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/46.0.2486.0 Mobile Safari/537.36 Edge/13.10586 false
综上, 在iPhone和Android上, 可以用micromessenger来判断, 而在WinPhone上, 可以用webbrowser来判断.
var isInWeChat = /(micromessenger|webbrowser)/.test(navigator.userAgent.toLocaleLowerCase());
如果你感兴趣的话, 可以通过打开 http://whatsmyuseragent.com/ 查看你的UA.