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Starter#Promises#Polyfill
Promise.all Polyfill
Implement your own Promise.all polyfill to understand how concurrent Promise handling works under the hood.
By modernDev2025-12-22Medium
Promise.all is one of the most powerful Promise utility methods in JavaScript. It allows you to execute multiple Promises concurrently and wait for all of them to complete. Understanding how it works internally is crucial for mastering asynchronous JavaScript.
In this challenge, you'll implement a polyfill for Promise.all from scratch. This will deepen your understanding of:
- How Promises work internally
- Concurrent vs sequential execution
- Error handling in Promise chains
- Maintaining order of results regardless of completion order
- Fail-fast behavior when any Promise rejects
Goal: Implement a Promise.all polyfill that handles concurrent Promises, maintains order, and implements fail-fast error handling.
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