Zoom to fit all markers with Google Maps V3

// creating the map
var map = new google.maps.Map(document.getElementById("map_canvas"), {
  mapTypeId: google.maps.MapTypeId.ROADMAP
});

// latitude, longitude values
var latLons = [ { lat: 35.6453962, lon: 139.7117893 }, 
                           { lat: 35.645076, lon: 139.709183 }  ];

// this is the bounding box container
var bounds = new google.maps.LatLngBounds();

// iterating through the points
latLons.forEach( function (element, index, array) {

  var point = new google.maps.LatLng(element.lat,element.lon);
  
  // extending the bounding box
  bounds.extend(point);

  // creating the marker on the map
  var marker = new google.maps.Marker({
        position: point,
        map: map
    });
});

// zooming on the map
map.fitBounds(bounds);