readme.md

cat line-delimitted-geo-data.json | node to-collection.js > valid-geojson.json

to-collection.js

var fs = require('fs');
var byline = require('byline');
var through2 = require('through2');

// write beginning of featurecollection
process.stdout.write('{"type":"FeatureCollection","features":[');

var first = true;

process.stdin
.pipe(byline.createStream())
.pipe(through2(function(chunk, enc, next){
  if (first) process.stdout.write(chunk.toString());
  else process.stdout.write(','+chunk.toString());
  first = false;
  next();
}))
.on('finish', function(){
  process.stdout.write(']}\n');
})