Introduction to Lowdb

Lowdb is a small local JSON database for Node.js, perfect for small projects and for situations where a full-fledged database is overkill. Lowdb provides a simple API for reading and writing JSON data and is powered by Lodash, making it versatile and highly optimized.

Installing Lowdb

  npm install lowdb

Creating a Simple Database

To begin, you need to include Lowdb and create an instance.

  
    const low = require('lowdb');
    const FileSync = require('lowdb/adapters/FileSync');
    const adapter = new FileSync('db.json');
    const db = low(adapter);
  

Setting Default Values

You can set some default values if your JSON file is empty.

  
    db.defaults({ posts: [], user: {}, count: 0 }).write();
  

Writing Data

Adding new data to the database is simple.

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

Reading Data

You can also read data from the database easily.

  
    const posts = db.get('posts').value();
    console.log(posts);
  

Updating Data

Updating existing data is straightforward.

  
    db.get('posts')
      .find({ id: 1 })
      .assign({ title: 'Lowdb is powerful!' })
      .write();
  

Removing Data

Removing data by filtering out what you don’t need.

  
    db.get('posts')
      .remove({ id: 1 })
      .write();
  

Using Third-Party Adapters

You can switch to other storage solutions using different adapters.

  
    const Memory = require('lowdb/adapters/Memory');
    const adapterMemory = new Memory();
    const dbMemory = low(adapterMemory);
  

API Examples with Applications

Let’s see how you can use Lowdb in a simple application.

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

    const app = express();
    const adapter = new FileSync('db.json');
    const db = low(adapter);
    db.defaults({ posts: [], user: {}, count: 0 }).write();

    app.use(express.json());

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

    app.post('/posts', (req, res) => {
      const newPost = req.body;
      db.get('posts')
        .push(newPost)
        .write();
      res.json(newPost);
    });

    app.put('/posts/:id', (req, res) => {
      const { id } = req.params;
      const updatedPost = req.body;
      db.get('posts')
        .find({ id: parseInt(id, 10) })
        .assign(updatedPost)
        .write();
      res.json(updatedPost);
    });

    app.delete('/posts/:id', (req, res) => {
      const { id } = req.params;
      db.get('posts')
        .remove({ id: parseInt(id, 10) })
        .write();
      res.status(204).send();
    });

    app.listen(3000, () => console.log('Server listening on port 3000'));
  

In this example, an Express.js server uses Lowdb to manage posts. The server supports CRUD operations with Lowdb, demonstrating how powerful and easy-to-use Lowdb is for fast and lightweight applications.

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