Introduction to lowdb

Lowdb is a small local JSON database powered by Lodash. It’s a simple and efficient way to persist data locally, without needing a large and complex database setup. Perfect for quick prototypes and small projects, lowdb allows you to read and write JSON data effortlessly.

In this article, we’ll explore various lowdb APIs and how to utilize them effectively. Let’s dive in!

Getting Started with lowdb

  const low = require('lowdb');
  const FileSync = require('lowdb/adapters/FileSync');
  
  const adapter = new FileSync('db.json');
  const db = low(adapter);
  
  // Set some defaults
  db.defaults({ posts: [], user: {}, count: 0 })
    .write();

Basic CRUD Operations

Create and Insert Data

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

Read Data

  // Get all posts
  const posts = db.get('posts')
    .value();
  
  // Get a single post by id
  const post = db.get('posts')
    .find({ id: 1 })
    .value();

Update Data

  // Update a post title
  db.get('posts')
    .find({ id: 1 })
    .assign({ title: 'lowdb is super awesome' })
    .write();

Delete Data

  // Remove a post
  db.get('posts')
    .remove({ id: 1 })
    .write();

Additional Useful API Examples

Handling Arrays

  // Increment count
  db.update('count', n => n + 1)
    .write();

Using Lodash Functions

  // Get the total number of posts
  const postCount = db.get('posts').size().value();

  // Get titles of all posts
  const titles = db.get('posts').map('title').value();

Working with Nested Data

  // Set user details
  db.set('user.name', 'typicode')
    .set('user.age', 30)
    .write();
  
  // Update nested data
  db.update('user.age', n => n + 1)
    .write();

App Example Using lowdb

Below is an example of a simple note-taking application using lowdb:

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

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

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

  app.use(express.json());

  app.get('/notes', (req, res) => {
    const notes = db.get('notes').value();
    res.send(notes);
  });

  app.post('/notes', (req, res) => {
    const note = req.body;
    db.get('notes').push(note).write();
    res.send(note);
  });

  app.delete('/notes/:id', (req, res) => {
    const id = req.params.id;
    db.get('notes').remove({ id: id }).write();
    res.send({ success: true });
  });

  app.listen(3000, () => {
    console.log('Server is running on port 3000');
  });

With this setup, you can start building more flexible and advanced functionality using lowdb.

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