<script type="text/javascript">

        window.onload = function() {

            isWeixinBrowser();

        }

        //判断是否微信浏览器

        function isWeixinBrowser() {

            var ua = navigator.userAgent.toLowerCase();

            var result = (/micromessenger/.test(ua)) ? true : false;

            if (result) {

                console.log('你正在访问微信浏览器');

            }

            else {

                console.log('你访问的不是微信浏览器');

            }

            return result;

        }

    </script>

<script type="text/javascript">

    function isWeiXin(){

        var ua = window.navigator.userAgent.toLowerCase();

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

            return true;

        }else{

            return false;

        }

    } 

    window.onload = function(){

        if(isWeiXin()){

            var p = document.getElementsByTagName('p');

            p[].innerHTML = window.navigator.userAgent;

        }

    } 

    </script>