@emstack/request

Lightweight, fetch-based HTTP client for TypeScript projects with strict typing, composable adapters, and interceptor/hook pipelines.

Highlights

• Zero runtime dependencies
• Strict TypeScript-first API
• Browser and Node.js support (via adapter resolution)
• Request and response interceptors
• Lifecycle hooks: beforeRequest, afterResponse, beforeError
• Built-in adapter decorators:
  • RetryAdapter (retry with fixed or exponential backoff)
  • CacheAdapter (TTL in-memory response cache)
  • DedupeAdapter (collapse concurrent identical requests)
• Query serialization with configurable array formats

Installation

pnpm add @emstack/request
# or
npm install @emstack/request

Quick Start

import { HttpClient } from '@emstack/request';

const client = new HttpClient({ baseURL: 'https://api.example.com' });

type User = { id: number; name: string; email: string };

const response = await client.get<User>('/users/1');
const user = await response.json();

Core Concepts

1) Typed request/response flow

type CreateUserRequest = { name: string; email: string };
type CreateUserResponse = { id: number; name: string; email: string };

const response = await client.post<CreateUserResponse, CreateUserRequest>(
  '/users',
  { name: 'Ada', email: 'ada@example.com' },
);

const created = await response.json();

2) Interceptors

Request interceptors run in LIFO order. Response interceptors run in FIFO order.

client.interceptors.request.use((config) => ({
  ...config,
  headers: {
    ...config.headers,
    authorization: 'Bearer my-token',
  },
}));

client.interceptors.response.use((res) => res);

3) Lifecycle hooks

const hookedClient = new HttpClient({
  baseURL: 'https://api.example.com',
  hooks: {
    beforeRequest: [
      (config) => {
        console.log('Sending:', config.method, config.url);
      },
    ],
    afterResponse: [
      (response, config) => {
        console.log('Received:', response.status, config.url);
      },
    ],
    beforeError: [
      (error, config) => {
        console.error('Failed:', config.url, error.message);
      },
    ],
  },
});

4) Adapter composition

import {
  HttpClient,
  AdapterResolver,
  CacheAdapter,
  DedupeAdapter,
  RetryAdapter,
  BackoffStrategy,
} from '@emstack/request';

const adapter = new CacheAdapter(
  new DedupeAdapter(
    new RetryAdapter(AdapterResolver.resolve(), {
      maxRetries: 3,
      delay: 100,
      backoff: BackoffStrategy.exponential,
    }),
  ),
  { ttl: 60_000 },
);

const resilientClient = new HttpClient({ baseURL: 'https://api.example.com' }, adapter);

Error Handling

import { HttpError, NetworkError, TimeoutError } from '@emstack/request';

try {
  await client.get('/health', { timeout: 3_000 });
} catch (error) {
  if (error instanceof TimeoutError) {
    console.error('Request timed out');
  } else if (error instanceof NetworkError) {
    console.error('Network failure');
  } else if (error instanceof HttpError) {
    console.error('HTTP error:', error.status);
  }
}

Available Exports

Main API includes:

• Core: HttpClient, HttpRequest, HttpResponse
• Adapters: AdapterResolver, RetryAdapter, CacheAdapter, DedupeAdapter, MemoryCacheStore
• Utilities: QuerySerializer
• Errors: HttpError, NetworkError, TimeoutError
• Types: RequestConfig, HttpClientConfig, QueryParams, HttpMethod, and related interfaces

See src/index.ts for the full export surface.

Development

Requirements

• Node.js 18+
• pnpm 9+

Scripts

pnpm dev            # Run Vite dev server
pnpm build          # Type-check and build library to dist/
pnpm test           # Run tests once
pnpm test:watch     # Run tests in watch mode
pnpm test:coverage  # Generate coverage report
pnpm lint           # Lint source files
pnpm lint:fix       # Auto-fix lint issues
pnpm format         # Format source and markdown files

Local setup

pnpm install
pnpm test
pnpm build

Example Application

A sample React app demonstrating practical usage is available in examples/todo-app.

cd examples/todo-app
pnpm install
pnpm dev

Testing and Quality

• Unit tests are located under src/tests
• Coverage output is generated under coverage
• ESLint and Prettier are configured for consistent code quality

Release and Commit Conventions

• Commit linting uses Conventional Commits
• semantic-release is configured for automated releases

For contribution workflow, see CONTRIBUTING.md.

License

MIT. See LICENSE.