docs: function findRectangleIndexContainingPoint(rectangles, x, y) {
      let closestIdx;
      rectangles.some((d, idx) => {
        if ((d.x1 <= x && x <= d.x2) && (d.y1 <= y && y <= d.y2)) {
          closestIdx = idx;
          return true;
        }
        return false;
      });
      return closestIdx;
    }