let deferredPrompt;

// add to homescreen
window.addEventListener("beforeinstallprompt", (e) => {
    // Prevent Chrome 67 and earlier from automatically showing the prompt
    e.preventDefault();
    // Stash the event so it can be triggered later.
    deferredPrompt = e;
});

function isDeferredNotNull() {
    return deferredPrompt != null;
}

function presentAddToHome() {
    if (deferredPrompt != null) {
        // Update UI to notify the user they can add to home screen
        // Show the prompt
        deferredPrompt.prompt();
        // Wait for the user to respond to the prompt
        deferredPrompt.userChoice.then((choiceResult) => {
            if (choiceResult.outcome === "accepted") {
                console.log("User accepted the A2HS prompt");
            } else {
                console.log("User dismissed the A2HS prompt");
            }
            deferredPrompt = null;
        });
    } else {
        console.log("deferredPrompt is null");
        return null;
    }
}