local-mock-api

A simple async local mock API without backend.

✅ Designed for prototyping and fast iterations

✅ Simulate an async API effortlessly

✅ Based on localStorage

Installation

npm install local-mock-api

CRUD API

Factory

createApi<T>(namespace: string): Api<T>

Creates a scoped API instance using namespace as the localStorage key.

• Returns: CRUD methods for type T.

Methods

list(): Promise<T[]>

Fetch all stored items.

get(id: string): Promise<T | null>

Fetch a single item by id.

add(item: Omit<T, "id">): Promise<T>

Add a new item (auto-generates id).

delete(id: string): Promise<void>

Delete an item by id.

update(id: string, updates: Partial<Omit<T, "id">>): Promise<T | null>

Update specific fields of an item by id.

clearAll(): Promise<void>

Clear all data for the namespace.

Example (Single namespace)

/**
 * Prototyping with one namespace (Note).
 */
interface Note {
  id: string;
  content: string;
}

const noteApi = createApi<Note>("notes");

async function test() {
  const newNote = await noteApi.add({ content: "Learn ChatGPT tips" });
  console.log("Added:", newNote);

  const notes = await noteApi.list();
  console.log("All Notes:", notes);

  const fetched = await noteApi.get(newNote.id);
  console.log("Fetched:", fetched);

  const updated = await noteApi.update(newNote.id, {
    content: "Updated content",
  });
  console.log("Updated:", updated);

  await noteApi.delete(newNote.id);
  console.log("Deleted:", newNote.id);

  await noteApi.clearAll();
  console.log("Cleared all notes");
}

test();

Example (Multiple namespaces)

/**
 * Example usage of local-mock-api for prototyping
 * with two independent namespaces (Todo and Note).
 */

import { createApi } from "local-mock-api";

type Todo = { id: string; text: string; done: boolean };
type Note = { id: string; title: string; content: string };

const todoApi = createApi<Todo>("todos");
const noteApi = createApi<Note>("notes");

async function run() {
  console.log("\n=== TODOS ===");
  await todoApi.clearAll();
  const newTodo = await todoApi.add({ text: "Buy milk", done: false });
  console.log("Added todo:", newTodo);
  console.log("All todos:", await todoApi.list());
  const updatedTodo = await todoApi.update(newTodo.id, { done: true });
  console.log("Updated todo:", updatedTodo);
  await todoApi.delete(newTodo.id);
  console.log("Todo deleted. Remaining todos:", await todoApi.list());

  console.log("\n=== NOTES ===");
  await noteApi.clearAll();
  const newNote = await noteApi.add({
    title: "Meeting Notes",
    content: "Discuss project roadmap.",
  });
  console.log("Added note:", newNote);
  console.log("All notes:", await noteApi.list());
  const updatedNote = await noteApi.update(newNote.id, {
    content: "Updated project roadmap details.",
  });
  console.log("Updated note:", updatedNote);
  await noteApi.delete(newNote.id);
  console.log("Note deleted. Remaining notes:", await noteApi.list());

  console.log("\n✅ All done.");
}

run();