Node.js - jsonfile

Easily read/write JSON files in Node.js. Note: this module cannot be used in the browser.

Why?

Writing JSON.stringify() and then fs.writeFile() and JSON.parse() with fs.readFile() enclosed in try/catch blocks became annoying.

Installation

npm install --save jsonfile

Usage

Use the default export of jsonfile to work with the real on-disk file system.

const jsonfile = require('jsonfile')
jsonfile.readFile('/real/disk/location.json', (err, obj) => {
  if (err) console.error(err)
  console.dir(obj)
})

Advanced Usage

Use the attached JsonFile constructor to create unique instances of the API. This is mostly useful when you want to use a virtual or mock filesystem instead of the real filesystem.

The JsonFile constructor takes one argument: the underlying fs object to use. The supplied fs must be drop-in compatible with Node's fs object. Packages like memfs and unionfs would work.

const memfs = require('memfs')
const jsonfile = require('jsonfile')
const jf = new jsonfile.JsonFile(memfs)
jf.writeFileSync('/virtual.json', { not: 'a real file' });
jf.readFile('/virtual.json', (err, obj) => {
  obj.not === 'a real file'
})

API

• readFile(filename, [options], callback)
• readFileSync(filename, [options])
• writeFile(filename, obj, [options], callback)
• writeFileSync(filename, obj, [options])

readFile(filename, [options], callback)

options (object, default undefined): Pass in any fs.readFile options or set reviver for a JSON reviver.

• throws (boolean, default: true). If JSON.parse throws an error, pass this error to the callback. If false, returns null for the object.

const jsonfile = require('jsonfile')
const file = '/tmp/data.json'
jsonfile.readFile(file, function (err, obj) {
  if (err) console.error(err)
  console.dir(obj)
})

You can also use this method with promises. The readFile method will return a promise if you do not pass a callback function.

const jsonfile = require('jsonfile')
const file = '/tmp/data.json'
jsonfile.readFile(file)
  .then(obj => console.dir(obj))
  .catch(error => console.error(error))

readFileSync(filename, [options])

options (object, default undefined): Pass in any fs.readFileSync options or set reviver for a JSON reviver.

• throws (boolean, default: true). If an error is encountered reading or parsing the file, throw the error. If false, returns null for the object.

const jsonfile = require('jsonfile')
const file = '/tmp/data.json'

console.dir(jsonfile.readFileSync(file))

writeFile(filename, obj, [options], callback)

options: Pass in any fs.writeFile options or set replacer for a JSON replacer. Can also pass in spaces and override EOL string.

const jsonfile = require('jsonfile')

const file = '/tmp/data.json'
const obj = { name: 'JP' }

jsonfile.writeFile(file, obj, function (err) {
  if (err) console.error(err)
})

Or use with promises as follows:

const jsonfile = require('jsonfile')

const file = '/tmp/data.json'
const obj = { name: 'JP' }

jsonfile.writeFile(file, obj)
  .then(res => {
    console.log('Write complete')
  })
  .catch(error => console.error(error))

formatting with spaces:

const jsonfile = require('jsonfile')

const file = '/tmp/data.json'
const obj = { name: 'JP' }

jsonfile.writeFile(file, obj, { spaces: 2 }, function (err) {
  if (err) console.error(err)
})

overriding EOL:

const jsonfile = require('jsonfile')

const file = '/tmp/data.json'
const obj = { name: 'JP' }

jsonfile.writeFile(file, obj, { spaces: 2, EOL: '\r\n' }, function (err) {
  if (err) console.error(err)
})

appending to an existing JSON file:

You can use fs.writeFile option { flag: 'a' } to achieve this.

const jsonfile = require('jsonfile')

const file = '/tmp/mayAlreadyExistedData.json'
const obj = { name: 'JP' }

jsonfile.writeFile(file, obj, { flag: 'a' }, function (err) {
  if (err) console.error(err)
})

writeFileSync(filename, obj, [options])

options: Pass in any fs.writeFileSync options or set replacer for a JSON replacer. Can also pass in spaces and override EOL string.

const jsonfile = require('jsonfile')

const file = '/tmp/data.json'
const obj = { name: 'JP' }

jsonfile.writeFileSync(file, obj)

formatting with spaces:

const jsonfile = require('jsonfile')

const file = '/tmp/data.json'
const obj = { name: 'JP' }

jsonfile.writeFileSync(file, obj, { spaces: 2 })

overriding EOL:

const jsonfile = require('jsonfile')

const file = '/tmp/data.json'
const obj = { name: 'JP' }

jsonfile.writeFileSync(file, obj, { spaces: 2, EOL: '\r\n' })

appending to an existing JSON file:

You can use fs.writeFileSync option { flag: 'a' } to achieve this.

const jsonfile = require('jsonfile')

const file = '/tmp/mayAlreadyExistedData.json'
const obj = { name: 'JP' }

jsonfile.writeFileSync(file, obj, { flag: 'a' })

License

(MIT License)

Copyright 2012-2016, JP Richardson [email protected]