Js判定移动端是否安装app,若已安装，则打开，未安装则跳转到下载页面

<script type="text/javascript">
document.getElementById('openApp').onclick = function(e){

if(navigator.userAgent.match(/(iPhone|iPod|iPad);?/i))
{
window.location.href = "com.baidu.tieba://";//ios app协议(如：com.baidu.tieba://)
window.setTimeout(function() {
window.location.href = "https://itunes.apple.com/cn/app/id477927812"; //跳转到App store
}, 2000)
}
if(navigator.userAgent.match(/android/i))
{
window.location.href = "com.baidu.tieba://app";//android app协议(如：com.baidu.tieba://app)
window.setTimeout(function() {
window.location.href = "https://****.apk";//android 下载地址
}, 2000)
}
};
</script>