jsonfile

What is jsonfile?

The jsonfile npm package is a simple JSON file reading and writing library for Node.js. It provides utility functions to read and write JSON files with ease, handling the asynchronous file system operations and JSON parsing/stringifying under the hood.

What are jsonfile's main functionalities?

Reading JSON files

This feature allows you to read JSON files asynchronously. The readFile function takes a file path and a callback function that receives an error or the parsed JSON object.

const jsonfile = require('jsonfile');

jsonfile.readFile('/path/to/file.json', (err, obj) => {
  if (err) console.error(err);
  console.log(obj);
});

Writing JSON files

This feature allows you to write JSON objects to files asynchronously. The writeFile function takes a file path, the object to be written, and a callback function that is called upon completion or error.

const jsonfile = require('jsonfile');

const obj = {name: 'John', age: 30};
jsonfile.writeFile('/path/to/file.json', obj, (err) => {
  if (err) console.error(err);
});

Reading JSON files synchronously

This feature allows you to read JSON files synchronously, blocking the event loop until the file is read. The readFileSync function takes a file path and returns the parsed JSON object or throws an error.

const jsonfile = require('jsonfile');

try {
  const obj = jsonfile.readFileSync('/path/to/file.json');
  console.log(obj);
} catch (err) {
  console.error(err);
}

Writing JSON files synchronously

This feature allows you to write JSON objects to files synchronously, blocking the event loop until the file is written. The writeFileSync function takes a file path and the object to be written, and it will throw an error if the operation fails.

const jsonfile = require('jsonfile');

const obj = {name: 'Jane', age: 25};
try {
  jsonfile.writeFileSync('/path/to/file.json', obj);
} catch (err) {
  console.error(err);
}

Customizing JSON spacing

This feature allows you to customize the indentation of the JSON output. The writeFile and writeFileSync functions accept an options object where you can specify the number of spaces to use for indentation.

const jsonfile = require('jsonfile');

const obj = {name: 'Alice', age: 28};
jsonfile.writeFile('/path/to/file.json', obj, {spaces: 2}, (err) => {
  if (err) console.error(err);
});

Other packages similar to jsonfile

fs-extra

fs-extra is a package that builds on the native fs module, providing additional methods and functionality. It includes methods for JSON file handling similar to jsonfile, such as readJson, writeJson, readJsonSync, and writeJsonSync. fs-extra offers a broader set of file system operations, making it a more comprehensive choice for general file system tasks.

fs-jetpack

fs-jetpack is another file system library that offers a fluent API for file operations. It includes read and write functionalities for JSON files with methods like readAsync, writeAsync, read, and write. fs-jetpack provides a different API design and additional file manipulation methods, which might be preferred by some developers for its convenience and chaining capabilities.

README

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

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 [e-mail]