🎯 Promise.all() Implementation
Category: js / promises
Difficulty: hard
Interview Importance: 🔴 Critical — Implementing Promise.all is one of the most common JavaScript interview questions. Tests understanding of promises, async handling, and edge cases. 1️⃣ What is Promise.all? Promise.all takes an iterable (usually an array) of promises and returns a single promise that: Resolves when ALL input promises resolve -> returns array of results in order Rejects immediately when ANY promise rejects -> returns the first rejection reason [code example] Visual Behavior [code example] 2️⃣ Why Use Promise.all? Use Cases Without Promise.all Sequential: slow One-by-one Complex chaining Manual tracking Performance Benefit [code example]...