merge GeoJSON quick&dirty

gistfile1.js

var fs = require('fs');
var files = process.argv.slice(2);
var output = { type: 'LineString', coordinates: [ ] };
for (var i = 0; i < files.length; ++i) {
  output.coordinates.append(JSON.parse(fs.readFileSync(files[i])).coordinates);
}
fs.writeFileSync('output.json', JSON.stringify(output, null, '\t'));