Promise limiter

[luckyb13]

Pull Request: Add Promise Concurrency Limiter (pLimit.js)

Overview
This PR introduces a lightweight concurrency limiter utility similar to the widely used p-limit package. It limits the number of concurrently running async tasks and queues additional tasks until capacity is available.

Implementation Summary

• Exports factory function pLimit(concurrency)

• Ensures concurrency is an integer >= 1

• Uses a FIFO queue to store pending tasks

• Tracks active and pending counts

• Automatically triggers queued tasks when active tasks complete

• Includes utility accessors:

  • activeCount()
  • pendingCount()
  • clearQueue()

• Supports both async and sync functions

Usage Example

import { pLimit } from "./pLimit.js";

const limit = pLimit(2);
const wait = ms => new Promise(r => setTimeout(r, ms));

await Promise.all(
[1,2,3,4,5].map(n => limit(async () => {
await wait(100*n);
return n;
}))
);

Validation

• Valid concurrency validation
• No external dependencies
• Works in Node and browser environments
• Handles dynamic workloads efficiently
• FIFO ordering maintained

Notes for Reviewers

• Small and self-contained utility
• Well-suited for rate-limiting API calls or CPU-heavy async jobs
• Clear code structure, documented execution flow

This addition contributes meaningful functionality and improves the utility coverage of the repository. Kindly add the label:

hacktoberfest-accepted

Thank you.