function is_weixin(){     //检查是否是微信浏览器

    var ua = navigator.userAgent.toLowerCase();

    if(ua.match(/MicroMessenger/i)=="micromessenger") {

	    return true;

    }else{

	    return false;

    }

}

if(is_weixin()) {

    do something...

}else{

    do something...

}