Google Map : Join Polygons

map.js

// Import JSTS : http://bjornharrtell.github.io/jsts/
// Import Google Map API

var map = new google.maps.Map(document.getElementById('map'), {
  mapTypeId: google.maps.MapTypeId.TERRAIN
});

var bound = new google.maps.LatLngBounds();

var paths = [
  // Polygon 1
  [
    {lat: 0.00000, lng: 0.00000},
    {lat: 0.00000, lng: 0.00000},
    {lat: 0.00000, lng: 0.00000},
    {lat: 0.00000, lng: 0.00000},
  ],
  // Polygon 2
  [
    {lat: 0.00000, lng: 0.00000},
    {lat: 0.00000, lng: 0.00000},
    {lat: 0.00000, lng: 0.00000},
    {lat: 0.00000, lng: 0.00000},
  ],
  // Polygon 3
  [
    {lat: 0.00000, lng: 0.00000},
    {lat: 0.00000, lng: 0.00000},
    {lat: 0.00000, lng: 0.00000},
    {lat: 0.00000, lng: 0.00000},
  ]
];

for(var i in paths) {
  for(var z in paths[i]) {
    bound.extend(paths[i][z]);
  }
}

var polygonPath = mergePath(paths);

new google.maps.Polygon({
    map: map,
    paths: polygonPath,
    strokeColor: '#000',
    strokeOpacity: 0.3,
    strokeWeight: 2,
    fillColor: '#0000FF',
    fillOpacity: 0.8
});

map.fitBounds(bound);

function mergePath(paths) {
    var polyUnion = null;
    var geometryFactory = new jsts.geom.GeometryFactory();

    for(var i in paths) {
        var linearRing = [];

        for(var z in paths[i]) {
            linearRing.push(
                new jsts.geom.Coordinate(paths[i][z].lat, paths[i][z].lng)
            );
        }

        var jtspoly = geometryFactory.createPolygon(geometryFactory.createLinearRing(linearRing));
        jtspoly.normalize();

        if(polyUnion == null) {
            polyUnion = jtspoly;
        } else {
            polyUnion = polyUnion.union(jtspoly);
        }

    }

    var path = [];
    var coordinates = polyUnion.getCoordinates();
    for(var i in coordinates) {
        path.push(new google.maps.LatLng(coordinates[i].x, coordinates[i].y));
    }

    return path;
}