How to use @turf/projection - 2 common examples

});
        return featureCollection(results);
    }

    // Project GeoJSON to Transverse Mercator projection (convert to Meters)
    var projected;
    var bbox = turfBbox(geojson);
    var needsTransverseMercator = bbox[1] > 50 && bbox[3] > 50;

    if (needsTransverseMercator) {
        projected = {
            type: geometry.type,
            coordinates: projectCoords(geometry.coordinates, defineProjection(geometry))
        };
    } else {
        projected = toMercator(geometry);
    }

    // JSTS buffer operation
    var reader = new GeoJSONReader();
    var geom = reader.read(projected);
    var distance = radiansToLength(lengthToRadians(radius, units), 'meters');
    var buffered = BufferOp.bufferOp(geom, distance);
    var writer = new GeoJSONWriter();
    buffered = writer.write(buffered);

    // Detect if empty geometries
    if (coordsIsNaN(buffered.coordinates)) return undefined;

    // Unproject coordinates (convert to Degrees)
    var result;
    if (needsTransverseMercator) {

var buffered = BufferOp.bufferOp(geom, distance);
    var writer = new GeoJSONWriter();
    buffered = writer.write(buffered);

    // Detect if empty geometries
    if (coordsIsNaN(buffered.coordinates)) return undefined;

    // Unproject coordinates (convert to Degrees)
    var result;
    if (needsTransverseMercator) {
        result = {
            type: buffered.type,
            coordinates: unprojectCoords(buffered.coordinates, defineProjection(geometry))
        };
    } else {
        result = toWgs84(buffered);
    }

    return (result.geometry) ? result : feature(result, properties);
}