IronDB is the best way to store persistent key-value data in the browser. Data saved to IronDB is redundantly saved to multiple browser stores

• Cookies
• IndexedDB
• LocalStorage
• SessionStorage

and relentlessly self heals if any of those stores are deleted or corrupted. In this way, IronDB is like Evercookie but

1. Is actively maintained and well documented.

2. Provides a simple, modern, Promise-based API.

3. Strikes an equitable balance between reliability and respect for the user. Data is stored resiliently but can also be voluntarily purged if the user designedly clears cookies and application storage.

4. Doesn't use nefarious exploits nor deprecated third party plugins like Flash, Silverlight, or Java. Only standard, ratified HTML5 APIs are used.

5. Doesn't vandalize performance or the user experience. For example, Evercookie's CSS History Knocking can beget a deluge of background HTTP requests, and loading Silverlight or Flash can thrash the user's disk or raise unsought permission modals.

When you store a key-value pair in IronDB, that key and value are saved redundantly in the browser's cookie, IndexedDB, LocalStorage, and SessionStorage storage engines.

When a value is retrieved via its key, IronDB

1. Looks up that key in every store.
2. Counts each unique, returned value.
3. Determines the most commonly returned value as the 'correct' value.
4. Returns this most common correct value

Then IronDB self heals: if any store(s) returned a value different than the determined correct value, or no value at all, the correct value is rewritten to that store. In this way, consensus, reliability, and redundancy is maintained.

IronDB's API is simple. To store a value, use set(key, value):

import { IronDB } from 'iron-db'

await IronDB.set('key', 'value')

key and value must be DOMStrings. IronDB.set(key, value) also always returns value, so it can be chained or embedded, like

const count = (await IronDB.set('count', countNumberOfClowns())) + 1

To retrieve a value, use get(key, default=null):

const value = await IronDB.get('key', default=null)

get() returns the value associated with key, if key exists. If key doesn't exist, default is returned. key must be a DOMString.

Finally, to remove a key, use remove(key):

IronDB.set('hi', 'bonjour')
console.log(await IronDB.get('hi'))  // Prints 'bonjour'.

await IronDB.remove('key')

console.log(await IronDB.get('hi')) // Prints 'null'.

key must be a DOMString.

The storage engines that IronDB stores data in can also be configured. For example, to only store data reliably in browser cookies and localStorage:

import { IronStorage, CookieStore, LocalStorageStore } from 'iron-db'

const stores = [new CookieStore(), new LocalStorageStore()]
const db = IronStorage(stores)

await db.set('key', JSON.Stringify({1:1}))

Available stores are

• CookieStore -> Data stored in document.cookie.
• IndexedDbStore -> Data stored in window.indexedDB.
• LocalStorageStore -> Data stored in window.localStorage.
• SessionStorageStore -> Data stored in window.sessionStorage.

Adding other additional, custom stores is easy, too: new stores need only implement the get(key), set(key, value), and remove(key) methods.

Installing IronDB with npm is easy.

$ npm install iron-db