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)) {
var loadDateTime = new Date();
window.setTimeout(function() {
var timeOutDateTime = new Date();
if(timeOutDateTime - loadDateTime < 5000) {
window.location = "要跳转的下载app页面URL";
} else {
window.close();
}
},25);
window.location = " apps custom url schemes ";
} else if(navigator.userAgent.match(/android/i)) {
var loadDateTime = new Date();
var state = window.open("apps custom url schemes ", '_blank');
window.setTimeout(function() {
var timeOutDateTime = new Date();
if(timeOutDateTime - loadDateTime < 5000) {
window.location = "要跳转的下载app页面URL";
} else {
window.close();
}
},25);
}
}