geojson-merge
Merge multiple GeoJSON files into one FeatureCollection.
install
npm install geojson-merge
api
merge([geojson, geojson2...])
Merges GeoJSON objects (geometry, feature, or featurecollection) into one FeatureCollection.
cli
npm install -g geojson-merge
geojson-merge file.geojson otherfile.geojson > combined.geojson