H5中调起微信这么实现，如果未安装则提示未安装

<!DOCTYPE html>

<html>

    <head>

        <meta charset="UTF-8">

        <meta name="viewport" content="width=device-width,minimum-scale=1.0,maximum-scale=1.0,user-scalable=no">

        <title>判断手机是否安装微信</title>

    </head>

    <body>

    <a href="javascript:testApp('weixin://')" class="dl-btn" id="download">打开微信</a>

    <script>

    function testApp(url) {

          var timeout, t = 1000, hasApp = true;

          setTimeout(function () {

            if (!hasApp) {

                //没有安装微信

                var r=confirm("您没有安装微信，请先安装微信!");

                if (r==true){

                    location.href="http://weixin.qq.com/"

                }

            }else{

                //安装微信

            }

            document.body.removeChild(ifr);

          }, 2000) 

          var t1 = Date.now();

          var ifr = document.createElement("iframe");

          ifr.setAttribute('src', url);

          ifr.setAttribute('style', 'display:none');

          document.body.appendChild(ifr);

          timeout = setTimeout(function () {

             var t2 = Date.now();

             if (!t1 || t2 - t1 < t + 100) {

               hasApp = false;

             }

          }, t);

        }

    </script>

    </body>

</html>