var polygons = {
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "properties": {},
      "geometry": {
        "type": "Polygon",
        "coordinates": [[
          [-67.031021, 10.458102],
          [-67.031021, 10.53372],
          [-66.929397, 10.53372],
          [-66.929397, 10.458102],
          [-67.031021, 10.458102]
        ]]
      }
    }, {
      "type": "Feature",
      "properties": {},
      "geometry": {
        "type": "Polygon",
        "coordinates": [[
          [-66.919784, 10.397325],
          [-66.919784, 10.513467],
          [-66.805114, 10.513467],
          [-66.805114, 10.397325],
          [-66.919784, 10.397325]
        ]]
      }
    }
  ]
};
 
var area = turf.area(polygons);
 
//=area