Принятый ответ, переписанный в ES6:

$(document).ready(() => {
  const mapEl = $('#our_map').get(0); // OR document.getElementById('our_map');

  // Display a map on the page
  const map = new google.maps.Map(mapEl, { mapTypeId: 'roadmap' });

  const buildings = [
    {
      title: 'London Eye, London', 
      coordinates: [51.503454, -0.119562],
      info: 'carousel'
    },
    {
      title: 'Palace of Westminster, London', 
      coordinates: [51.499633, -0.124755],
      info: 'palace'
    }
  ];

  placeBuildingsOnMap(buildings, map);
});


const placeBuildingsOnMap = (buildings, map) => {
  // Loop through our array of buildings & place each one on the map  
  const bounds = new google.maps.LatLngBounds();
  buildings.forEach((building) => {
    const position = { lat: building.coordinates[0], lng: building.coordinates[1] }
    // Stretch our bounds to the newly found marker position
    bounds.extend(position);

    const marker = new google.maps.Marker({
      position: position,
      map: map,
      title: building.title
    });

    const infoWindow = new google.maps.InfoWindow();
    // Allow each marker to have an info window
    google.maps.event.addListener(marker, 'click', () => {
      infoWindow.setContent(building.info);
      infoWindow.open(map, marker);
    })

    // Automatically center the map fitting all markers on the screen
    map.fitBounds(bounds);
  })
})