lowdb

What is lowdb?

Lowdb is a small local JSON database for Node, Electron, and the browser. It's a simple and lightweight way to store data locally using a JSON file. It is ideal for small projects, quick prototypes, and applications that do not require a full-fledged database.

What are lowdb's main functionalities?

Create and Read Data

This feature allows you to create and read data from a JSON file. The code initializes a lowdb instance, sets default values, adds a new post, and retrieves it.

const low = require('lowdb');
const FileSync = require('lowdb/adapters/FileSync');

const adapter = new FileSync('db.json');
const db = low(adapter);

db.defaults({ posts: [] }).write();

db.get('posts').push({ id: 1, title: 'lowdb is awesome' }).write();

const post = db.get('posts').find({ id: 1 }).value();
console.log(post);

Update Data

This feature allows you to update existing data in the JSON file. The code updates the title of the post with id 1 and retrieves the updated post.

db.get('posts').find({ id: 1 }).assign({ title: 'lowdb is super awesome' }).write();
const updatedPost = db.get('posts').find({ id: 1 }).value();
console.log(updatedPost);

Delete Data

This feature allows you to delete data from the JSON file. The code removes the post with id 1 and retrieves the remaining posts.

db.get('posts').remove({ id: 1 }).write();
const posts = db.get('posts').value();
console.log(posts);

Other packages similar to lowdb

nedb

NeDB is a lightweight JavaScript database that is similar to MongoDB but is meant for small projects. It supports indexing and querying and can be used both in Node.js and in the browser. Compared to lowdb, NeDB offers more advanced querying capabilities and indexing.

lokijs

LokiJS is a fast, in-memory database for Node.js and browsers. It is designed for performance and can handle large datasets efficiently. LokiJS offers more advanced features like indexing, binary serialization, and live querying compared to lowdb.

json-server

json-server is a full fake REST API with zero coding in less than 30 seconds. It is ideal for quick prototyping and mocking REST APIs. Unlike lowdb, json-server is more focused on providing a RESTful interface to your JSON data.

README

LowDB

Flat JSON file database for Node

• Serverless
• Multiple databases
• In-memory or disk-based
• 80+ methods from Lo-Dash API
• Asynchronous and fault-tolerant writing
• Extendable

LowDB uses Lo-Dash functional programming API instead of a MongoDB-like API. This makes it quite unique and different.

LowDB powers JSON Server and JSONPlaceholder. If you need something similar for the browser, check Underscore-db.

Usage

var low = require('lowdb')
var db = low('db.json')

db('songs').push({ title: 'low!'})

Database is automatically created and saved to db.json in a readable format.

{
  "songs": [
    {
      "title": "low!"
    }
  ]
}

Data can be queried and manipulated using any Lo-Dash method.

var song = db('songs').find({ title: 'low!' }).value()
db('songs').remove({ title: 'low!' })

You can also use id-based methods by extending LowDB with Underscore-db.

API

low([filename])

Creates a disk-based or in-memory database instance. If a filename is provided, it loads or creates it.

var db = low()          // in-memory
var db = low('db.json') // disk-based

low.mixin(source)

Use it to extend Lo-Dash globally with your own utility functions or third-party libraries.

// Must be called before calling db('songs') for functions to be available.
low.mixin({
  second: function(array) {
    if (array.length >= 2) return array[1]
  }
})

var song = db('songs').second().value()

low.stringify(obj) and low.parse(str)

Overwrite these methods to customize JSON stringifying and parsing.

db.object

Database object. Useful if you want to access the content of your JSON file and don't want to go through Lo-Dash methods.

console.log(db.object) // { songs: [ { title: 'low!' } ] }
db('songs').value() === db.object.songs

db.save()

LowDB automatically saves to disk. However, in case you directly modify the content of the database object, you'll need to manually call save.

delete db.object.songs
db.save()

Documentation

Operations

With LowDB you get access to the entire Lo-Dash API, so there's many, many ways to query and manipulate data. Here are a few examples to get you started.

Sort the top five songs.

db('songs')
  .where({published: true})
  .sortBy('views')
  .first(5)
  .value()

Retrieve song titles.

db('songs')
  .pluck('titles')
  .value()

Get the number of songs.

db('songs').size()

Make a deep clone of songs.

db('songs').cloneDeep().value

Update a song.

db('songs').find({ title: 'low!' }).assign({ title: 'hi!'})

Remove songs.

db('songs').remove({ title: 'low!' })

Id-based resources support

Being able to retrieve data using an id can be quite useful, particularly in servers. To add id-based resources support to LowDB, you have 2 options.

Underscore-db provides a set of helpers for creating and manipulating id-based resources.

low.mixin(require('underscore-db'))

var db = low('db.json')

var songId = db('songs').insert({ title: 'low!' }).value().id
var song   = db('songs').get(songId).value()

Or simply use uuid.

var uuid = require('uuid')

var songId = db('songs').push({ id: uuid(), title: 'low!' }).value().id
var song   = db('songs').find({ id: songId }).value()

In both cases, your db.json will then look like this.

{
  "songs": [
    {
      "id": "e31aa48c-a9d8-4f79-9fce-ded4c16c3c4c",
      "title": "low!"
    }
  ]
}

Changelog

See details changes for each version in the release notes.

Limits

LowDB is a convenient method for storing data without setting up a database server. It's fast enough and safe to be used as an embedded database.

However, if you need high performance and scalability more than simplicity, you should stick to databases like MongoDB.

License

LowDB is released under the MIT License.