OpalDB

OpalDB is a minimal in-memory database with zero dependencies written in JavaScript for Node.js. It is primarily for learning and demonstration purposes and as such should not be considered production ready.

Models

First make a schema for your records, then convert that schema into a model, and then create records.

const opal = require('opal')
const Schema = opal.Schema;
const Model = opal.Model;

const person = new Schema({
  name: 'STRING',
  age: 'NUMBER',
  hobbies: 'ARRAY'
})

const PersonModel = opal.model(person)

const joe = new PersonModel({
  name: 'Joe Shmoe',
  age: 28,
  hobbies: ['soccer', 'baseball']
})

The schema does simple validation and the model provides an onBeforeSave hook.

const bob = new PersonModel({
  name: 'Bob',
  age: 23,
  hobbies: 'Baskeball, etc'
})
// The above code will throw an error because hobbies is not an array.

UserModel.onBeforeSave((record) => {
  record.password = hashAndSalt(record.password)
})
// Now our users will have secure passwords.

Tables

First create a database, then add a table to it, then insert records into the table.

const db = new opal.Database()

db.addTable('people')

db.in('people').insert(joe)

Events

You can add listeners for insert, update and delete.

db.in('people').listen('insert', (record) => {
  console.log(record)
})

Queries

Queries at the table level include getById and findWhere. The former is a quick table lookup and the latter is an expensive match between the records in the database and the object passed into the findWhere function. You can also delete by index which is fairly straightforward.

db.in('people').getById(0) // returns Joe

db.in('people').findWhere({ name: 'Joe Shmoe' }) // also returns Joe

db.in('people').delete(0) // deletes Joe

Use the 'where' method to return a query on a property of the records in a specific table. The 'where' method returns a query object that has type specific methods for matching records.

// .contains() only works with array properties
db.in('people').where('hobbies').contains('soccer')

// .lessThan() and .greaterThan() work with number properties
db.in('people').where('age').lessThan(30)

// .equals() works with numbers and string but not arrays
db.in('people').where('name').equals('Joe')

For nested records, the 'where' method can take an array of properties.

db.in('people').where(['address', 'city']).equals('Palo Alto')

Secondary indexes

You can create an index from any attribute on a record.

db.in('people').createIndex('name')
db.in('people').getByIndex('name', 'Joe') // returns all the people named Joe