JS如何检测手机上APP是否安装的情况

if (navigator.userAgent.match(/android/i)) {
     // 通过iframe的方式试图打开APP，如果能正常打开，会直接切换到APP，并自动阻止a标签的默认行为
     // 否则打开a标签的href链接
     var isInstalled;
     //下面是安卓端APP接口调用的地址，自己根据情况去修改
     var ifrSrc = 'AppProtocolHeader://camnpr? type=0&id=${com.id}&phone_num=${com.phone_num}';
     var ifr = document.createElement('iframe');
     ifr.src = ifrSrc;
     ifr.style.display = 'none';
     ifr.onload = function() {
     // alert('Is installed.');
     isInstalled = true;
     alert(isInstalled);
     document.getElementById('openApp0').click();};
     ifr.onerror = function() {
         // alert('May be not installed.');
         isInstalled = false;
         alert(isInstalled);
     }
     document.body.appendChild(ifr);
     setTimeout(function() {
         document.body.removeChild(ifr);
     },1000);
}

//ios判断
if (navigator.userAgent.match(/(iPhone|iPod|iPad);?/i))
     if (navigator.userAgent.match(/(iPhone|iPod|iPad);?/i))  {
         //Animation://com.camnpr.animation
         var isInstalled;
         //var gz = '{"comName":"${com.short_name}","comID":"${com.id}","comPhoneNum":"${com.phone_num}","type":"0"}';
         //var jsongz =JSON.parse(gz);

         //下面是IOS调用的地址，自己根据情况去修改
         var ifrSrc = 'AppProtocolHeader://?comName=${com.short_name}&comID=${com.id}&comPhoneNum=${com.phone_num}&type=0';var ifr = document.createElement('iframe');
         ifr.src = ifrSrc;
         ifr.style.display = 'none';
         ifr.onload = function() {
              // alert('Is installed.');
              isInstalled = true;
              alert(isInstalled);
              document.getElementById('openApp1').click();};
         ifr.onerror = function() {
              // alert('May be not installed.');
              isInstalled = false;
              alert(isInstalled);
         }
         document.body.appendChild(ifr);
         setTimeout(function() {
              document.body.removeChild(ifr);
         },1000);
     }
}