Node.js simple JSON database

const Promise = require('bluebird');
const fs = Promise.promisifyAll(require('fs'));
const path = require('path');
const dbPath = path.join(__dirname, 'db.json');

const factoryDefaults = {
  defaultPrefix: ";",
  servers: []
}

class Server {
  constructor(id) {
    this.id = id;
  }
}

function saveJSON(jsonObject) {
  fs.writeFileSync(dbPath, JSON.stringify(jsonObject, null, 2), 'utf-8');
}

function getDB() {
  return new Promise(async resolve => {
    let data = await fs.readFileAsync(dbPath);
    try {
      let json = JSON.parse(data);
      resolve(json);
    } catch (ex) {
      saveJSON(factoryDefaults);
      resolve(factoryDefaults);
    }
  });
}

function getValue(key) {
  return new Promise(async resolve => {
    let json = await getDB();
    if (typeof json[key] !== "undefined")
      resolve(json[key]);
    else throw new Error(`Key ${key} doesn't exist in the database.`);
  });
}

function editValue(key, value) {
  return new Promise(async resolve => {
    let db = await getDB();
    db[key] = value;
    saveJSON(db);
  });
}

module.exports = {
  getDB: getDB,
  getValue: getValue,
  editValue: editValue
}