JSONLog

json-log.js

import fsExtra from 'fs-extra'

export default function jsonLog (filepath) {
  return async function (data) {
    await fsExtra.ensureFile(filepath)
    await fsExtra.appendFile(filepath, JSON.stringify(data) + '\n')
  }
}

json-log.test.js

import test from 'ava'
import path from 'path'
import os from 'os'
import fs from 'fs'

import jsonLog from '../json-log.js'

test('writes json to a file', async t => {
  const filepath = path.join(os.tmpdir(), 'test-' + Math.random() + '.txt')

  const logger = jsonLog(filepath)

  await logger({ fields: 'example', problems: [1, 2, 3] })
  await logger({ fields: 'example2', problems: [1, 2, 3] })

  const file = fs.readFileSync(filepath, 'utf-8')

  t.is(file, `{"fields":"example","problems":[1,2,3]}\n{"fields":"example2","problems":[1,2,3]}\n`)
})