Dirty hack to merge geoJSON feature.

mergeFeatures.js

// Sample use: node mergeFeatures.js argentina.json buenos_aires.json > argentina_merged.json

var origin1 = require(path.resolve(__dirname, process.argv[2])),
    origin2 = require(path.resolve(__dirname, process.argv[3])),
    destination = {
  	"type": "FeatureCollection",
		"features": []
	};

destination.features = origin1.features.concat(origin2.features);

console.log(

    JSON.stringify(destination)

);