lodat

lodat (Local Database)

Powerful persistent store for Javascript. Compatible with (localStorage, sessionStorage, AsyncStorage, and many more)

Installation

npm install lodat --save

Getting started

Making a simple counter app using Lodat

import lodat from "lodat";
 
// create lodat db with some options
const db = lodat({
  // by default, lodat stores data in memory
  // in this case, we want to store data in localStorage,
  // of course, we can specify other storages: sessionStorage, AsyncStorage or customized storage
  storage: localStorage,
  // specify initial data
  initial: { count: 1 },
  // this action will be called after db created
  // note: this is a functional generator, we will take a look at this later on (please refer Generator Function)
  *init() {
    render();
  },
});
// handle db updating
db.subscribe(render);
 
function* getCount({ get }) {
  return yield get("count");
}
 
function* increase({ set }) {
  yield set("count", (prev) => prev + 1);
}
 
async function render() {
  const count = await db.exec(getCount);
  document.body.innerHTML = `<h1>Counter: ${count}</h1>`;
}
 
setInterval(() => {
  db.exec(increase);
}, 1000);

Using schema

import lodat from "lodat";
 
const db = lodat({
  schemas: {
    // "todos" is context prop name, its map to "todo" schema
    todos: "todo",
  },
});
 
function* addTodo(context) {
  return yield context.todos.create({ title: "new todo" });
}
 
function* removeTodo(context, key) {
  yield context.todos.remove(key);
}
 
const newTodo = await db.exec(addTodo);
 
db.exec(removeTodo, newTodo.key);

Querying entity

function* getCompletedTodos(context) {
  return yield context.todos.all((todo) => todo.completed);
}
 
function* getFirstCompletedTodos(context) {
  return yield context.todos.get((todo) => todo.completed);
}
 
function* getTodoByKey(context, key) {
  return yield context.todos.get(key);
}

Storing data in cookie

import { CookieStorage } from "cookie-storage";
 
const db = lodat({ storage: new CookieStorage() });

Examples

1. Todo App

Performance testing (TBD)

Lodat is about 10x faster than lowdb Add and update 1000 todos

References

lodat(options)

• options:

  name	type	description
  name	string	database name (def = '')
  storage	Storage object	specify storage type will be used (def = memoryStorage)
  debounce	number	specify writing debouncing (def = 0, no debouncing)
  initial	any	specify default data
  init	Generator Function	specify an action will be executed in initializing phase
  schemas	string[]	list of schema names
  schemas	{ prop: 'schema name' }	schema mappings

• Return: Database instance

Database props

name	return	description
exec(executor, payload?)	Promise	execute an executor with specified payload. Executor must be Generator Function
subscribe(listener)	Unsubscribe function	add a change listener. It will be called any time an data manipulated
clear()	void	clear all data
flush()	void	flush all pending writes to storage

Context props

name	type/return	description
schema(name)	Schema object	get specified schema by its name
get(name)	Yield	get value of specified database prop
set(name, value)	Yield	set value of specified database prop
set(name, reducerFn)	Yield	set value of specified database prop using reducerFn, the reducerFn retrieves previous value as first argument
exec(executor, payload?)	Yield	execute an executor with specified payload. Executor must be Generator Function
fork(executor, payload?)	Yield	execute an executor with specified payload and dont block current execution. Executor must be Generator Function

Schema props

name	type/return	description
name	string	schema name
create(props)	Yield	create new entity with specified props
exist(entityKey)	Yield	check entity existing by its key
remove(...entityKeys)	Yield	remove multiple entities by their keys
count()	Yield	return a number of entity in the schema
all()	Yield<Entity[]>	return all entities in the schema
all(limit)	Yield<Entity[]>	return first N entities in the schema
all(entityKeys)	Yield<Entity[]>	return all entities that matches given keys
all(predicateFn)	Yield<Entity[]>	return all entities that matches given predicateFn
all(predicateFn, limit)	Yield<Entity[]>	return first N entities that matches given predicateFn
get(entityKey)	Yield	get entity by key
get(predicateFn)	Yield	get first entity that matches given predicateFn
clear()	Yield	clear all entities in the schema
update(entity, props)	Yield	update specified entity with new props, if no props changed, nothing to write to storage
subscribe(listener)	Unsubscribe function	add a change listener. It will be called any time an entity manipulated

Generator Function

Lodat uses generator function to control reading or writing data flows and async execution (no async/await needed). Below is simple generator function.

function* generatorFunction(generatorContext, payload) {
  // a generatorContext provides many util methods, please refer Context props section for further info
  // retrieve return value from yield expression
  const returnValueOfDoSomething = yield generatorContext.doSomething(payload);
  // retrieve resolved value from promise
  const resolvedValue = yield ApiCall(payload);
}