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@vp-tw/nanostores-storage

createMemoryAdapter

Creates an in-memory storage adapter. Data is stored in JavaScript memory and lost on page refresh.

Use Cases

  • Testing — Isolated storage for each test
  • SSR — Server-side rendering where browser APIs aren’t available
  • Demos — Interactive examples without polluting real storage

Try it in the createStorageStore Demo — select “memoryAdapter” when creating a store.

Usage

The memory adapter is built-in and can be imported directly:

import { createStorageStore, createMemoryAdapter } from "@vp-tw/nanostores-storage";


const memoryAdapter = createMemoryAdapter();


const store = createStorageStore(memoryAdapter, "test-key", {
  defaultValue: "initial",
});


store.set("updated");
console.log(store.get()); // "updated"


// Data is isolated to this adapter instance

Pre-populated Data

You can initialize with existing data:

import { createMemoryAdapter } from "@vp-tw/nanostores-storage";


const adapter = createMemoryAdapter({
  theme: "dark",
  language: "en",
});


console.log(adapter.get("theme")); // "dark"

Testing Example

import { describe, it, expect, beforeEach } from "vitest";
import { createStorageStore, createMemoryAdapter } from "@vp-tw/nanostores-storage";


describe("my feature", () => {
  let adapter: ReturnType<typeof createMemoryAdapter>;


  beforeEach(() => {
    // Fresh adapter for each test
    adapter = createMemoryAdapter();
  });


  it("stores user preference", () => {
    const store = createStorageStore(adapter, "theme", {
      defaultValue: "light",
    });


    store.set("dark");
    expect(store.get()).toBe("dark");
  });


  it("starts fresh each test", () => {
    const store = createStorageStore(adapter, "theme", {
      defaultValue: "light",
    });


    // Previous test's data is gone
    expect(store.get()).toBe("light");
  });
});

SSR Example

stores.ts
import {
  createStorageStore,
  localStorageAdapter,
  createMemoryAdapter,
} from "@vp-tw/nanostores-storage";


// Use memory adapter on server, localStorage on client
const adapter = typeof window === "undefined" ? createMemoryAdapter() : localStorageAdapter;


export const themeStore = createStorageStore(adapter, "theme", {
  defaultValue: "system",
});

Singleton Pattern

If you need shared memory storage across your app:

memory-adapter.ts
import type { StorageAdapter } from "@vp-tw/nanostores-storage";
import { createMemoryAdapter } from "@vp-tw/nanostores-storage";


let instance: StorageAdapter | null = null;


export function getMemoryAdapter(): StorageAdapter {
  if (!instance) {
    instance = createMemoryAdapter();
  }
  return instance;
}


export function resetMemoryAdapter(): void {
  instance = null;
}

See Also