e required.
        map = new google.maps.Map(document.getElementById('map'), {
          center: {lat: 40.7413549, lng: -73.9980244},
          zoom: 13,
          styles: styles,
          mapTypeControl: false
        });

        // These are the real estate listings that will be shown to the user.
        // Normally we'd have these in a database instead.
        var locations = [
          {title: 'Park Ave Penthouse', location: {lat: 40.7713024, lng: -73.9632393}},
          {title: 'Chelsea Loft', l