Return Center polygon in google maps v3. This does not apply to some shapes though. I recommend using turf.js instead https://turfjs.org/

polygonCenter.js

function polygonCenter(poly) {
    var lowx,
        highx,
        lowy,
        highy,
        lats = [],
        lngs = [],
        vertices = poly.getPath();

    for(var i=0; i<vertices.length; i++) {
      lngs.push(vertices.getAt(i).lng());
      lats.push(vertices.getAt(i).lat());
    }

    lats.sort();
    lngs.sort();
    lowx = lats[0];
    highx = lats[vertices.length - 1];
    lowy = lngs[0];
    highy = lngs[vertices.length - 1];
    center_x = lowx + ((highx-lowx) / 2);
    center_y = lowy + ((highy - lowy) / 2);
    return (new google.maps.LatLng(center_x, center_y));
  }

A great solution or https://arxiv.org/ftp/arxiv/papers/1212/1212.3193.pdf

it works fine! thanks!

That's great. You can also check this function turf.centerOfMass or centroid
https://turfjs.org/docs/#centerOfMass