ts-souko

ts-souko is a library for constructing type-safe Storage wrapper, for TypeScript.

souko(倉庫) is a Japanese word stands for "warehouse", or "storage".

Installation

By npm:

npm i ts-souko

By yarn:

yarn add ts-souko

Basic Usage

import { createTypedStorage, codecs, baseStorages } from 'ts-souko';

// Creating typed wrapper for localStorage.
// For each key, specify the `Codec` for the type of corresponding value.
const storage = createTypedStorage({
  id: codecs.number,
  name: codecs.string,
}, { base: baseStorages.webLocal } );

// Now, type of value is inferred as you specify key!
storage.set('id', 100);       // OK
storage.set('name', 'Alice'); // OK
storage.set('id', 'nan');     // type error!
storage.set('name', 0);       // type error!
storage.set('unknown', null); // type error!

const i = storage.get('id');      // i: number | null
const n = storage.get('name');    // n: string | null
const x = storage.get('unknown'); // type error!

Features

Type-safety and Developer Experience

Using ts-souko, you can get type-safety on string value storages by minimum code. Moreover, together with VS Code's powerful integration with TypeScript, you can get maximum developer experience on coding using storages. TypeScript compiler will be always on your side!

With ts-souko, you won't be troubled with problems like:

• What keys are available on the storage?
• What type of value is expected for that key?
• What type should you convert the value from storage to?

Flexibility and Extensibility by Abstractions

ts-souko defines 2 abstractions: BaseStorage and Codec. They make ts-souko flexible and extensible.

• BaseStorage is abstraction of "string key - string value" storage. This enables you to use ts-souko on any storage that has ability to store string value with string key associated, not limited to browser's localStorage or sessionStorage!

  • "Async" version is also supported (AsyncTypedStorage on AsyncBaseStorage). This is useful to interact with storages that expose async API, such as React Native Async Storage or Capacitor Storage.

• Codec<T> is abstraction about conversion between value of type T and it's string representation, back and forth. This enables you to store and retrieve values of arbitrary type to/from storage in arbitrary format, with safety. For example, you can write Codec for array of numbers that converts an array as "slash(/) separated values":

import { codecs, createTypedStorage } from 'ts-souko';

// note: codecs.number implements value-preserving conversion for numbers.
const slashSeparatedNumsCodec: Codec<number[]> = {
  encode: (a: number[]): string => 
    a.map(e => codecs.number.encode(e)).join('/'),

  decode: (s: string): number[] =>
    s.split('/').map(e => codecs.number.decode(e))
}

const ts = createTypedStorage({
  ssv: slashSeparatedNumsCodec, 
}, { ... });

ts.set('ssv', [1, 2, 3]) // OK. stores: '1/2/3' 
ts.get('ssv')            // => [1, 2, 3]

ts.set('ssv', ["a", "b"]) // type error!

Built-in Interoperability with Schema Validation Libraries

Via Codec abstraction, you can write code that retrieve value from storage with schema validations using a library like io-ts. Fortunately, you don't have to write own Codec with validations! ts-souko is equipped with built-in Codec interoperate with popular schema validation libraries:

Library Name	Codec
io-ts	codecs.jsonWithIoTs(iotsType, reporter?)
superstruct	codecs.jsonWithSuperstruct(struct)
zod	codecs.jsonWithZod(zod)

Example using ts-souko with io-ts:

import { codecs, createTypedStorage } from 'ts-souko';
import * as t from 'io-ts';

const User = t.type({
  userId: t.number,
  name: t.string,
});
type User = t.TypeOf<typeof User>;

const userCodec = codecs.jsonWithIoTs(User);
const ts = crateTypedStorage({
  user: userCodec,
}, { ... });

const u: User = { userId: 1, name: 'Alice' };
ts.set('user', u) // OK
ts.get('user')    // === `u`

ts.set('user', { userId: '1', namee: 'Alice' }) // type error, of course.

If you couldn't find your favorite validation library, you can still use codecs.jsonWithValidation(validate), where validate is function implements custom validation logic.

API Document

see Here.