Google Map with several markers are not displayed

Hello,
In laravel 5.8 app I add Google Map with several markers and I have empty block and no errors in console
and no map acttually is visible
In function with code:

frontendTimeline.prototype.initEventsListingMap = function () {

    console.log("this_mapEvents::")
    console.log( this_mapEvents )

    $("#div_map_wrapper").css("display","block")

    var map = new google.maps.Map(document.getElementById('div_map'), {
        zoom: 12,
        mapTypeControlOptions: {
            mapTypeIds: [google.maps.MapTypeId.SATELLITE, google.maps.MapTypeId.ROADMAP, google.maps.MapTypeId.HYBRID]
        },
        mapTypeId: google.maps.MapTypeId.ROADMAP,
    });

    this_mapEvents.map((mapEvent,index) => {

        if ( typeof mapEvent.longitude != "undefined" && mapEvent.longitude != null && typeof mapEvent.latitude != "undefined" && mapEvent.latitude != null ) {
            console.log("INSIDE map::")
            console.log( map )

            var markerPosition = {lat: parseFloat(mapEvent.latitude), lng: parseFloat(mapEvent.longitude)};
            var infowindow = new google.maps.InfoWindow({
                content: mapEvent.event_name + ": <strong>" + mapEvent.event_start_date + "-" + mapEvent.event_end_date + "</strong>"
            });

            var marker = new google.maps.Marker({
                position: markerPosition,
                draggable: false,

                map: map
            });
            google.maps.event.addListener(marker, 'mouseover', function () {
                infowindow.open(map, marker);
            });
        } // if ( typeof mapEvent.longitude != "undefined" && mapEvent.longitude != null && typeof mapEvent.latitude != "undefined" && mapEvent.latitude != null ) {

    });

Code (JavaScript):

live : https://www.votes.my-demo-apps.tk/events-timeline
in console it is visible that 2 markers are added .

I have a very similar page with 1 marker https://www.votes.my-demo-apps.tk/event/rest-on-the-lake
which works ok.
Why error in first case and how to fix it ?

Thanks!

 

Sorry, no ideas why map is emoty ?