Mastering Promise Concurrency: Alternatives to Promise.all in JavaScript

In JavaScript, Promise.all is a popular method for handling concurrent promises, but it has a clear limitation—if any promise fails, the entire operation fails. Moreover, it provides no way to limit the number of concurrent executions, which can overload system resources. This article examines several elegant alternatives for managing concurrency limits.

Why Limit Concurrency?

Limiting the number of concurrent operations is especially important in the following scenarios:

API rate limits

Prevent server overload

Reduce memory usage

Improve system stability

Limitations of Promise.all

The issues with this approach are:

All promises run simultaneously without concurrency limits

Any single promise failure causes the entire operation to fail

Cannot track the progress of individual promises

Elegant Alternatives

1. Promise.allSettled

Introduced in ES2020, Promise.allSettled can wait for all promises to settle (whether fulfilled or rejected):

This solves the error‑handling issue but still does not address concurrency limits.

2. Simple Queue Implementation

This approach creates a concurrency‑limited queue that controls how many promises run at once, though it still leaves room for improvement.

For more complex requirements, mature libraries such as p-limit can implement concurrency control more succinctly.