var bufferOp = function(feature, radius) {
  var reader = new jsts.io.GeoJSONReader();
  var geom = reader.read(JSON.stringify(feature.geometry));
  var buffered = geom.buffer(radius);
  var parser = new jsts.io.GeoJSONParser();
  buffered = parser.write(buffered);

  return {
    type: 'Feature',
    geometry: buffered,
    properties: {}
  };
};