通过user-agent判断h5页⾯是在哪个⼿机App（QQ、、⽀
付宝）下打开的
function getAppClient(){
  var ua = LowerCase();
  if(ua.match(/MicroMessenger/i)=="micromessenger") {
  return "weixin";
  } else if (ua.match(/QQ/i) == "qq") {
  return "QQ";
  }else if(ua.match(/AlipayClient/i) == 'alipayclient'){网络连接失败
  return "Alipay";
  }else{
  ...
  }
}