docs: function(polygon) {
    const area = getArea(polygon);
    let output;
    if (area > 10000) {
      output = (Math.round(area / 1000000 * 100) / 100) +
          ' ' + 'km<sup>2</sup>';
    } else {
      output = (Math.round(area * 100) / 100) +
          ' ' + 'm<sup>2</sup>';
    }
    return output;
  }