Request Manager

Overview

A lightweight TypeScript library for handling request deduplication. Only the latest request's result will be returned, previous requests' results will be ignored. Note that this does not actually cancel the underlying requests - they continue to execute in the background.

Features

• Request Deduplication: Automatically ignores results from superseded requests when a new one is made
• Error Handling: Properly handles errors from the latest request while ignoring errors from superseded requests
• TypeScript Support: Full TypeScript type definitions
• Lightweight: Minimal overhead with no external dependencies
• Easy to Use: Simple API that wraps any async function

Installation

npm install seq-request

Usage

Basic Usage

import { RequestManager } from 'seq-request';

const requestManager = new RequestManager();

// Wrap your async function
const wrappedRequest = requestManager.wrap(async (id: string) => {
  const response = await fetch(`/api/data/${id}`);
  return response.json();
});

// Use the wrapped function
const result = await wrappedRequest('123');

Handling Multiple Requests

const requestManager = new RequestManager();
const wrappedRequest = requestManager.wrap(async (id: string) => {
  await new Promise(resolve => setTimeout(resolve, 1000)); // Simulate slow request
  return `Result for ${id}`;
});

// First request (result will be ignored)
const promise1 = wrappedRequest('1');
// Second request (result will be ignored)
const promise2 = wrappedRequest('2');
// Third request (result will be returned)
const promise3 = wrappedRequest('3');

const [result1, result2, result3] = await Promise.all([promise1, promise2, promise3]);
console.log(result1); // null (superseded)
console.log(result2); // null (superseded)
console.log(result3); // "Result for 3" (latest request)

Error Handling

const requestManager = new RequestManager();
const wrappedRequest = requestManager.wrap(async () => {
  throw new Error('Request failed');
});

try {
  await wrappedRequest();
} catch (error) {
  console.error('Latest request failed:', error.message);
}

API Reference

RequestManager

Constructor

new RequestManager()

Creates a new RequestManager instance.

Methods

wrap(requestFn: Function)

Wraps a function to add request deduplication functionality.

Parameters:

• requestFn - The function to wrap (can be async or sync)

Returns:

• A wrapped function that ignores results from superseded requests

Behavior:

• Only the most recent call to the wrapped function will return its result
• Previous calls will return null (for successful requests) or be ignored (for failed requests)
• Errors from the latest request are properly thrown
• Errors from superseded requests are ignored
• Important: The underlying requests are not actually cancelled - they continue to execute in the background

Examples

Search Input with Debouncing

const requestManager = new RequestManager();
const searchAPI = requestManager.wrap(async (query: string) => {
  const response = await fetch(`/api/search?q=${encodeURIComponent(query)}`);
  return response.json();
});

// User types quickly
searchAPI('a');     // Result ignored
searchAPI('ab');    // Result ignored
searchAPI('abc');   // Only this result is returned

Form Submission

const requestManager = new RequestManager();
const submitForm = requestManager.wrap(async (formData: FormData) => {
  const response = await fetch('/api/submit', {
    method: 'POST',
    body: formData
  });
  return response.json();
});

// Prevent multiple submissions from returning results
const result = await submitForm(formData);

Important Notes

• No Actual Cancellation: This library does not cancel the underlying requests. They continue to execute in the background, which means:
  • Network requests will still complete
  • Server-side operations will still run
  • Resources may still be consumed
• Result Filtering: The library only filters which results are returned to your application
• Use Cases: Best suited for scenarios where you want to ignore stale results, not for resource management

Development

Install Dependencies

pnpm install

Run Tests

npm run test

Build

npm run build

Development Mode

npm run dev

Feature improve

• [ ] Enable to cancel older request
• [ ] Add request timeout support
• [ ] Add request retry mechanism
• [ ] Add request caching support

License

MIT