js判断手机是否安装了某一款app，有则打开，没有去下载

function openApp() {
         if (navigator.userAgent.match(/(iPhone|iPod|iPad);?/i)) {
            letloadDateTime = new Date();
            window.setTimeout(function() {
               let timeOutDateTime = new Date();
               if (timeOutDateTime - loadDateTime < 5000) {
                  // 跳转至app下载页 以微信为例
                  window.location = "http://sj.qq.com/myapp/detail.htm?apkName=com.tencent.mm";
               } else {
                  window.close();
               }
            }, 25);
            // 打开本地的app 以微信为例
            window.location = "wexin://";
         } else if (navigator.userAgent.match(/android/i)) {
            let loadDateTime = new Date();
            window.setTimeout(function() {
               let timeOutDateTime = new Date();
               if (timeOutDateTime - loadDateTime < 5000) {
                  // 跳转至app下载页
                  window.location = "http://sj.qq.com/myapp/detail.htm?apkName=com.tencent.mm";
               } else {
                  window.close();
               }
            }, 25);
            // 打开本地的app
            window.location = "wexin://";
         }
      }

简写为

function openApp() {
	let loadDateTime = new Date();
            window.setTimeout(function() {
               let timeOutDateTime = new Date();
               if (timeOutDateTime - loadDateTime < 5000) {
                  // 跳转至app下载页 以微信为例
                  window.location = "http://sj.qq.com/myapp/detail.htm?apkName=com.tencent.mm";
               } else {
                  window.close();
               }
            }, 25);
            // 打开本地的app 以微信为例
            window.location = "wexin://";
}