Promise Pool

type Task<T> = () => Promise<T>;type ProgressCallback = (completed: number, total: number) => void;class PromisePool<T = any> {  private concurrency: number;  private tasks: Task<T>[];  private results: T[] = [];  private errors: Error[] = [];  constructor(concurrency: number = 3) {    this.concurrency = concurrency;    this.tasks = [];  }  add(task: Task<T>): this {    this.tasks.push(task);    return this;  }  async execute(onProgress?: ProgressCallback): Promise<{ results: T[]; errors: Error[] }> {    this.results = [];    this.errors = [];        const executing: Promise<void>[] = [];    let completed = 0;        for (const task of this.tasks) {      const promise = task()        .then(result => {          this.results.push(result);          completed++;          onProgress?.(completed, this.tasks.length);        })        .catch(error => {          this.errors.push(error instanceof Error ? error : new Error(String(error)));          completed++;          onProgress?.(completed, this.tasks.length);        })        .finally(() => {          executing.splice(executing.indexOf(promise), 1);        });            executing.push(promise);            if (executing.length >= this.concurrency) {        await Promise.race(executing);      }    }        await Promise.all(executing);        return { results: this.results, errors: this.errors };  }}export default PromisePool;

import PromisePool from './PromisePool';const pool = new PromisePool(3);const urls = ["https://api.example.com/data1", "https://api.example.com/data2", "https://api.example.com/data3"];urls.forEach(url => {  pool.add(() => fetch(url).then(r => r.json()));});const { results, errors } = await pool.execute((completed, total) => {  console.log(`Progress: ${completed}/${total}`);});console.log(`Completed: ${results.length} successful, ${errors.length} errors`);