Convert Elasticsearch "hits" JSON response to NDJSON format for easy importing back to Elasticsearch

hits2ndjson.js

#!/usr/bin/env node

const fs = require('fs')

const [ fileName ] = process.argv.slice(2)

if (fileName == null) {
  console.error('input file with search response required')
  process.exit(0)
}

const contents = fs.readFileSync(fileName, 'utf-8')
const json = JSON.parse(contents)
const hits = json.hits.hits

const output = hits.map(hit => JSON.stringify(hit._source)).join('\n')

console.log(output)