geojson-merge.js

var StreamConcat = require('stream-concat')
var geojsonStream = require('geojson-stream')
var glob = require('glob')
var fs = require('fs')
var log = require('single-line-log').stderr
var through2 = require('through2')
var config = require('./config.json')

var geoParse = geojsonStream.parse()
var geoStringify = geojsonStream.stringify()

var outputDirectory = config.outputDirectory
if (!fs.existsSync(outputDirectory)) {
	fs.mkdirSync(outputDirectory)
}
var w = fs.createWriteStream(`${outputDirectory}/output.geojson`)

var results = 0
var c = through2({
	objectMode: true
}, function(result, enc, callback) {
	results++
	log('Processing result: ' + results)
	this.push(result)
	callback()
})

glob('./geojson/*.geojson', function(er, files) {
	var streams = files.map(file => {
		return fs.createReadStream(file)
	})
	var streamIndex = 0
	var nextStream = function() {
		if (streamIndex === streams.length) return null 
		return streams[streamIndex++]
	}

	var combinedStream = new StreamConcat(nextStream, {
		objectMode: true
	})

	combinedStream.pipe(geoParse).pipe(c).pipe(geoStringify).pipe(w)
})