josdejong/csv42

csv42

A small and fast CSV parser with support for nested JSON.

Features

• 2 way: convert JSON to CSV and the other way around.
• Simple: straightforward and flexible API.
• Lightweight: 2KB gzipped with everything included, 1KB gzipped when only using json2csv.
• Fast: faster than the popular CSV libraries out there. See benchmark.
• Safe: handles inhomogeneous data, no risk of data loss.
• Modular: only load what you use, thanks to ES5 modules and a plugin architecture.
• Powerful:
  • Configurable properties: header, delimiter, eol.
  • Configurable fields, with custom value getters and setters and the ability to ignore fields.
  • Configurable serialization and deserialization of values via formatValue and parseValue.
  • Support for nested JSON objects: either flatten nested contents, or stringify as a JSON object.
• Standards compliant: adheres to the CSV standard RFC 4180.
• Universal: Created for the browser, but can be used in any JavaScript environment like node.js. TypeScript types included.

Note that the parser has no streaming support.

Why?

Well, you have to write a CSV parser at least once in you life, right? ;)

The csv42 library was developed specifically for https://jsoneditoronline.org, for use in the browser. Besides being small and fast, one important feature is supporting nested JSON objects. So, why the name csv42? Just because 42 is a beautiful number and to remind us that there is a whole universe of beautiful CSV libraries out there.

Install

npm install csv42

Usage

Install the library once:

Convert JSON to CSV

import { json2csv } from 'csv42'

const users = [
  { id: 1, name: 'Joe', address: { city: 'New York', street: '1st Ave' } },
  { id: 2, name: 'Sarah', address: { city: 'Manhattan', street: 'Spring street' } }
]

// By default, nested JSON properties are flattened
const csv = json2csv(users)
console.log(csv)
// id,name,address.city,address.street
// 1,Joe,New York,1st Ave
// 2,Sarah,Manhattan,Spring street

// You can turn off flattening using the option `flatten`
const csvFlat = json2csv(users, { flatten: false })
console.log(csvFlat)
// id,name,address
// 1,Joe,"{""city"":""New York"",""street"":""1st Ave""}"
// 2,Sarah,"{""city"":""Manhattan"",""street"":""Spring street""}"

// The CSV output can be fully customized and transformed using `fields`:
const csvCustom = json2csv(users, {
  fields: [
    { name: 'name', getValue: (item) => item.name },
    { name: 'address', getValue: (item) => item.address.city + ' - ' + object.address.street }
  ]
})
console.log(csvCustom)
// name,address
// Joe,New York - 1st Ave
// Sarah,Manhattan - Spring street

Convert CSV to JSON

import { csv2json } from 'csv42'

const csv = `id,name,address.city,address.street
1,Joe,New York,1st Ave
2,Sarah,Manhattan,Spring street`

// By default, fields containing a dot will be parsed inty nested JSON objects
const users = csv2json(csv)
console.log(users)
// [
//   { id: 1, name: 'Joe', address: { city: 'New York', street: '1st Ave' } },
//   { id: 2, name: 'Sarah', address: { city: 'Manhattan', street: 'Spring street' } }
// ]

// Creating nested objects can be turned off using the option `nested`
const usersFlat = csv2json(csv, { nested: false })
console.log(usersFlat)
// [
//   { id: 1, name: 'Joe', 'address.city': 'New York', 'address.street': '1st Ave' },
//   { id: 2, name: 'Sarah', 'address.city': 'Manhattan', 'address.street': 'Spring street' }
// ]

// The JSON output can be customized using `fields`
const usersCustom = csv2json(csv, {
  fields: [
    { name: 'name', setValue: (item, value) => (item.name = value) },
    { name: 'address.city', setValue: (item, value) => (item.city = value) }
  ]
})
console.log(usersCustom)
// [
//   { name: 'Joe', city: 'New York' },
//   { name: 'Sarah', city: 'Manhattan' }
// ]

API

json2csv<T>(json: T[], options?: CsvOptions<T>) : string

Where options is an object with the following properties:

A simple example of a ValueFormatter is the following. This formatter will enclose every value in quotes:

function formatValue(value: unknown): string {
  return '"' + String(value) + '"'
}

csv2json<T>(csv: string, options?: JsonOptions) : T[]

Where options is an object with the following properties:

A simple value parser can look as follows, parsing numeric values into numbers. This will keep all values as string:

function parseValue(value: string, quoted: boolean): unknown {
  const num = Number(value)
  return isNaN(num) ? value : num
}

Utility functions

The library exports a number of utility functions:

Alternatives

• https://www.npmjs.com/package/csv
• https://juanjodiaz.github.io/json2csv/
• https://www.npmjs.com/package/json-2-csv
• https://www.npmjs.com/package/papaparse
• https://www.npmjs.com/package/csvtojson
• https://www.npmjs.com/package/csv-stringify
• https://www.npmjs.com/package/csv-parser
• https://www.npmjs.com/package/fast-csv
• https://github.com/leeoniya/uDSV/
• Any many, many more...

Release

To release a new version:

$ npm run release

This will:

• lint
• test
• build
• increment the version number
• push the changes to git, add a git version tag
• publish the npm package

To try the build and see the change list without actually publishing:

$ npm run release-dry-run

License

csv42 is released as open source under the permissive the ISC license.

If you are using csv42 commercially, there is a social (but no legal) expectation that you help fund its maintenance. Start here.