A small local database powered by lodash API
Used by json-server and more than 70 awesome projects on npm.
const db = low('db.json')
db.defaults({ posts: [], user: {} })
.value()
db.get('posts')
.push({ id: 1, title: 'lowdb is awesome'})
.value()
db.set('user.name', 'typicode')
.value()
Data is automatically saved to db.json
{
"posts": [
{ "id": 1, "title": "lowdb is awesome"}
],
"user": {
"name": "typicode"
}
}
And you can query it using lodash API
db.get('posts')
.find({ id: 1 })
.value()
Lowdb is perfect for CLIs, small servers, Electron apps and npm packages in general.
It supports Node, the browser and uses lodash API, so it's very simple to learn. Actually... you may already know how to use lowdb ๐
- Lodash API
- Minimal and simple to use
- Highly flexible
- Custom storage (file, browser, in-memory, ...)
- Custom format (JSON, BSON, YAML, XML, ...)
- Mixins (id support, ...)
- Read-only or write-only modes
- Encryption
Important lowdb doesn't support Cluster.
npm install lowdb --save
Alternatively, if you're using yarn
yarn add lowdb
A UMD build is also available on unpkg for testing and quick prototyping:
<script src="https://unpkg.com/lodash@4/lodash.min.js"></script>
<script src="https://unpkg.com/lowdb/dist/lowdb.min.js"></script>
<script>
var db = low('db')
</script>
low([source, [options])
source
string or null, will be passed to storageoptions
objectstorage
object, by defaultlowdb/lib/file-sync
orlowdb/lib/browser
.read
function or nullwrite
function or null
format
objectserialize
function, by defaultJSON.stringify
deserialize
function, by defaultJSON.parse
writeOnChange
boolean
Creates a lodash chain, you can use any lodash method on it. When .value()
is called data is saved using storage
.
You can use options
to configure how lowdb should persist data. Here are some examples:
// in-memory
low()
// persisted using async file storage
low('db.json', { storage: require('lowdb/lib/file-async') })
// persisted using a custom storage
low('some-source', { storage: require('./my-custom-storage') })
// write on change disabled
low('db.json', { writeOnChange: false })
// read-only
const fileSync = require('lowdb/lib/file-sync')
low('db.json', {
storage: {
read: fileSync.read
}
})
// write-only
low('db.json', {
storage: {
write: fileSync.write
}
})
db._
Database lodash instance. Use it to add your own utility functions or third-party mixins like underscore-contrib or underscore-db.
db._.mixin({
second: function(array) {
return array[1]
}
})
const post1 = db.get('posts').first().value()
const post2 = db.get('posts').second().value()
db.getState()
Use whenever you want to access the database state.
db.getState() // { posts: [ ... ] }
db.setState(newState)
Use it to drop database or set a new state (database will be automatically persisted).
const newState = {}
db.setState(newState)
db.write([source])
Persists database using storage.write
option. Depending on the storage, it may return a promise (for example, with `file-async').
By default, lowdb automatically calls it when database changes.
const db = low('db.json')
db.write() // writes to db.json
db.write('copy.json') // writes to copy.json
db.read([source])
Reads source using storage.read
option. Depending on the storage, it may return a promise.
const db = low('db.json')
db.read() // reads db.json
db.read('copy.json') // reads copy.json
With lowdb, you get access to the entire lodash API, so there are many ways to query and manipulate data. Here are a few examples to get you started.
Please note that data is returned by reference, this means that modifications to returned objects may change the database. To avoid such behaviour, you need to use .cloneDeep()
.
Also, the execution of methods is lazy, that is, execution is deferred until .value()
is called.
Check if posts exists.
db.has('posts')
.value()
Set posts.
db.set('posts', [])
.value()
Sort the top five posts.
db.get('posts')
.filter({published: true})
.sortBy('views')
.take(5)
.value()
Get post titles.
db.get('posts')
.map('title')
.value()
Get the number of posts.
db.get('posts')
.size()
.value()
Get the title of first post using a path.
db.get('posts[0].title')
.value()
Update a post.
db.get('posts')
.find({ title: 'low!' })
.assign({ title: 'hi!'})
.value()
Remove posts.
db.get('posts')
.remove({ title: 'low!' })
.value()
Make a deep clone of posts.
db.get('posts')
.cloneDeep()
.value()
Being able to get 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.
const db = low('db.json')
db._.mixin(require('underscore-db'))
const postId = db.get('posts').insert({ title: 'low!' }).value().id
const post = db.get('posts').getById(postId).value()
uuid is more minimalist and returns a unique id that you can use when creating resources.
const uuid = require('uuid')
const postId = db.get('posts').push({ id: uuid(), title: 'low!' }).value().id
const post = db.get('posts').find({ id: postId }).value()
low()
accepts custom storage or format. Simply create objects with read/write
or serialize/deserialize
methods. See src/browser.js
code source for a full example.
const myStorage = {
read: (source, deserialize) => // must return an object or a Promise
write: (source, obj, serialize) => // must return undefined or a Promise
}
const myFormat = {
serialize: (obj) => // must return data (usually string)
deserialize: (data) => // must return an object
}
low(source, {
storage: myStorage,
format: myFormat
})
Simply encrypt
and decrypt
data in format.serialize
and format.deserialize
methods.
For example, using cryptr:
const Cryptr = require("./cryptr"),
const cryptr = new Cryptr('my secret key')
const db = low('db.json', {
format: {
deserialize: (str) => {
const decrypted = cryptr.decrypt(str)
const obj = JSON.parse(decrypted)
return obj
},
serialize: (obj) => {
const str = JSON.stringify(obj)
const encrypted = cryptr.encrypt(str)
return encrypted
}
}
})
See changes for each version in the release notes.
lowdb is a convenient method for storing data without setting up a database server. It is fast enough and safe to be used as an embedded database.
However, if you seek high performance and scalability more than simplicity, you should probably stick to traditional databases like MongoDB.
MIT - Typicode