js 判断 微信浏览器

<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>