kv-ts

Features

• functional key-value storage interface
• runtime type-safe with io-ts's codec
• observable support with RxJS

Create Entry

import * as O from 'fp-ts/lib/Option'
import * as t from 'io-ts'
import { initEntry, LOCAL_STORAGE_STORE } from 'kv-ts'

// Init Entry for store
const entry = initEntry({
  key: 'key',
  codec: t.string,
  store: LOCAL_STORAGE_STORE,
}) // StoreEntry<A>

// Use the Entry
entry.set('hello world') // (a: A) => void
entry.get() // () => O.Option<A>
entry.clear() // () => void
entry.observe() // () => Observable<O.Option<A>>

type of StoreEntry<A> is derived by the io-ts's codec t.Type<A>.
you can store any type supported in typescript by defining codec, they would be (encode as/decode from) JSON string in runtime to get in touch with the store.

Apply expiry

Sometimes we need to store values with expire time, (for example, for cache usage). initEntryWithExpiry can do this for you automatically.

import { initEntryWithExpiry, LOCAL_STORAGE_STORE } from 'kv-ts'

const entry = initEntryWithExpiry({
  key: 'key',
  codec: t.string,
  store: LOCAL_STORAGE_STORE,
  expiry: 2000, // unit: mileseconds
})

When entry.set is called and 2 seconds passed, entry.get then can only retrieve O.none.

withDefault

you can create an Entry with default value:

import { pipe } from 'fp-ts/lib/pipeable'
import { initEntry, LOCAL_STORAGE_STORE, withDefault } from 'kv-ts'

const entry = pipe(
  initEntry({ key: 'key', codec: t.string, store: LOCAL_STORAGE_STORE }),
  withDefault(() => 'a'),
)
// Use the Entry
entry.set('hello world') // (a: A) => void
entry.get() // () => A
entry.clear() // () => void
entry.observe() // () => Observable<A>

Custom store

store does not define the storage itself, it defined how we do IO with the key-value storage in a minimum way.

export interface Store {
  /** get string for key */
  get: (k: string) => O.Option<string>
  /** set string for key */
  set: (k: string, a: string) => void
  /** delete string for key */
  clear: (k: string) => void
}

The lib includes several pre-defined store:

• LOCAL_STORAGE_STORE
• SESSION_STORAGE_STORE

here is how the LOCAL_STORAGE_STORE is implemented:

import * as O from 'fp-ts/lib/Option'
import { pipe } from 'fp-ts/lib/pipeable'

export const LOCAL_STORAGE_STORE: Store = {
  get: (k: string) =>
    pipe(
      localStorage.getItem(k),
      O.fromNullable,
    ),
  set: (k: string, a: string) => localStorage.setItem(k, a),
  clear: (k: string) => localStorage.removeItem(k),
}

That is to say, you can define any store you are using by implementing these three functions.