@iwsio/json-csv-node

@iwsio/json-csv-node

This package extends @iwsio/json-csv-core specifically targeting Node.JS to support streaming. It's all the same code as before, just moved around. You can read more about it on my blog.

Usage

Buffered (Converts to CSV with an in-memory data source)

const { toCsv, toCsvSync } = require('@iwsio/json-csv-node') // CJS
import { toCsv, toCsvSync } from '@iwsio/json-csv-node' // ESM

// as a promise
const csv = await toCsv(data, options) // toCsv returns Promise<string>

// optionally, you can use a classic callback instead
toCsv(data, options, function(err, csv) {...}))

// synchronous
const csv = toCsvSync(data, options) // toCsvSync returns string

Streaming (Converts a "row at a time" from a stream source)

When using the streaming API, you can pipe data to it in object mode.

const { toCsvStream } = require('@iwsio/json-csv-node') // CJS
import { toCsvStream } from '@iwsio/json-csv-node' // ESM

const things = [
  {name: 'thing1', age: 20},
  {name: 'thing2', age: 30},
  {name: 'thing3', age: 45}
]
Readable.from(things) // <readable source in object mode>
  .pipe(toCsvStream(options)) // transforms to string and emits lines
  .pipe(process.stdout) // anything Writable


// toCsvStream(options) supports classic callback (for backwards compatibility)
toCsvStream(options, (err, transform) => {
  Readable.from(things)
    .pipe(toCsvStream(options))
})

NOTE: All the aliases from previous versions remain intact.

I renamed this API mostly for cosmetics and to cleanup named exports for ES Modules. It made more sense to me to import { toCSV } from 'json-csv' rather than importing the default and calling its prop. (I've been doing a lot of Typescript lately). But all the original versions are kept intact and tests are in place to assert they work.

const jsonCsv = require('@iwsio/json-csv-node') // CJS
import jsonCsv, { toCSV, toCsvStream, buffered, stream } from '@iwsio/json-csv-node' // ESM

jsonCsv.buffered // buffered (promise or callback)
jsonCsv.bufferedSync // buffered synchronous (passthrough from core)
jsonCsv.stream // stream (or callback w/ stream)

jsonCsv.toCsv // buffered, returns promise, callback optional
jsonCsv.toCsvSync // buffered synchronous (passthrough from core)
jsonCsv.toCsvStream // stream, returns stream, callback optional

// These are deprecated
jsonCsv.csv // alias to toCsvStream (streamed)
jsonCsv.csvBuffered // alias to toCsv (buffered)

Options

{
  // field definitions for CSV export
  fields :
  [
    {
      // required: field name for source value
      name: 'string',

      // optional: column label for CSV header
      label: 'string',

      // optional: transform value before exporting
      transform: function(value) { return value; }
    }
  ],

  // Other default options:
  fieldSeparator: ",",
  ignoreHeader: false
}

Advanced Example

Here, you can see we're using a deeper set of objects for our source data, and we're using dot notation in the field definitions like: contact.name for the contact name.

const items = [
  {
    downloaded: false,
    contact: {
      company: 'Widgets, LLC',
      name: 'John Doe',
      email: '[e-mail]',
    },
    registration: {
      year: 2013,
      level: 3,
    },
  },
  {
    downloaded: true,
    contact: {
      company: 'Sprockets, LLC',
      name: 'Jane Doe',
      email: '[e-mail]',
    },
    registration: {
      year: 2013,
      level: 2,
    },
  },
]
const options = {
  fields: [
    {
      name: 'contact.company', // uses dot notation
      label: 'Company',
    },
    {
      name: 'contact.name',
      label: 'Name',
    },
    {
      name: 'contact.email',
      label: 'Email',
    },
    {
      name: 'downloaded',
      label: "Downloaded",
      transform: (v) => v ? 'downloaded' : 'pending',
    },
    {
      name: 'registration.year',
      label: 'Year',
    },
    {
      name: 'registration.level',
      label: 'Level',
      transform: (v) => {
        switch (v) {
          case 1: return 'Test 1'
          case 2: return 'Test 2'
          default: return 'Unknown'
        }
      },
    },
  ],
}

(async () => {
  let result = await toCsv(items, options)
  console.log(result)
})()

// OR synchronous

(() => {
  let result = toCsvSync(items, options)
  console.log(result)
})()

Output

Company,Name,Email,Downloaded,Year,Level
"Widgets, LLC",John Doe,[e-mail],pending,2013,Unknown
"Sprockets, LLC",Jane Doe,[e-mail],downloaded,2013,Test 2