examples

Examples

CLI

// cli.js
import { LowSync, JSONFileSync } from 'lowdb'

const title = process.argv[2]
const adapter = new JSONFileSync('file.json')
const db = new LowSync(adapter)

db.read()
db.data ||= { posts: [] }

db.data.posts.push({ title })

db.write()

$ node cli.js "hello world"
$ cat file.json
# { "posts": [ "title": "hello world" ] }

Browser

import { LowSync, LocalStorage } from 'lowdb'

const adapter = new LocalStorage('db')
const db = new LowSync(adapter)

db.read()
db.data ||= { posts: [] }

db.data.posts.push({ title: 'lowdb' })

db.write()

Server

Note if you're developing a local server and don't expect to get concurrent requests, it can be easier to use JSONFileSync adapter.

But if you need to avoid blocking requests, you can do so by using JSONFile adapter.

import express from 'express'
import { Low, JSONFile } from 'lowdb'

const app = express()
app.use(express.json())

const adapter = new JSONFile('db.json')
const db = new Low(adapter)
await db.read()
db.data ||= { posts: [] }

const { posts } = db.data

app.get('/posts/:id', async (req, res) => {
  const post = posts.find((p) => p.id === req.params.id)
  res.send(post)
})

app.post('/posts', async (req, res, next) => {
  const post = posts.push(req.body)
  await db.write()
  res.send(post)
})

app.listen(3000, () => {
  console.log('listening on port 3000')
})

In-memory

With this adapter, calling db.write() will do nothing. One use case for this adapter can be for tests.

import { LowSync, JSONFileSync, MemorySync }

const adapter =
  process.env.NODE_ENV === 'test' ? new MemorySync() : new FileSync('db.json')

const db = new LowSync(adapter)