PushNotificationSender.js

var apn = require('apn');

var options = {
    token: {
        key: './keys/AuthKey_XXXXXXXXXX.p8',
        keyId: "XXXXXXXXXX",
        teamId: "XXXXXXXXXX"
    },
    production: false
};

var apnProvider = new apn.Provider(options);

function sendPushNotification(body){

    var notification = new apn.Notification();

    notification.expiry = Math.floor(Date.now() / 1000) + 60; // Expires 1 min from now.
    notification.badge = 1;
    notification.alert =  body.alertMessage;
    notification.sound = "ping.aiff";
    notification.payload = body.payload;
    notification.topic = "<application bundle identifier>";

    // Generate this UUID and store that in DB to remove the notification in future
    notification.id = "a986cc6c-f5a6-11e9-802a-5aa538984bd8";
    
    // We can achieve the same feature using 'apns-collapse-id'.
    // 'apns-collapse-id' ID need to be set. apn library provides a collapseId 
    // property which is linked with 'apns-collapse-id'.
    // More Info: https://developer.apple.com/library/archive/documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/CommunicatingwithAPNs.html#//apple_ref/doc/uid/TP40008194-CH11-SW1
    // notification.collapseId = "a986cc6c-f5a6-11e9-802a-5aa538984bd8";

    apnProvider.send(notification, body.deviceToken).then( (result) => {
        console.log('APNS Response : \n', result);
        res.send('POST App Push Notification');
    });
});