p-map vs bluebird vs async vs q
JavaScript Promise Libraries
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JavaScript Promise Libraries

JavaScript Promise libraries are essential tools for handling asynchronous operations in a more manageable and readable way. They provide various utilities to work with promises, enabling developers to write cleaner code while avoiding callback hell. These libraries enhance the native Promise API, offering additional features such as concurrency control, error handling, and improved performance. By leveraging these libraries, developers can streamline their asynchronous workflows, making it easier to compose and manage complex asynchronous tasks in their applications.

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p-map72,083,7211,48221.3 kB114 months agoMIT
bluebird43,243,55020,757-1276 years agoMIT
async028,194808 kB242 years agoMIT
q015,227-115-MIT

Feature Comparison: p-map vs bluebird vs async vs q

Concurrency Control

  • p-map:

    P-map is specifically designed for concurrency control, allowing you to set a limit on how many promises are executed concurrently. This feature is essential for managing resources effectively when dealing with multiple asynchronous operations.

  • bluebird:

    Bluebird offers built-in support for concurrency control through methods like Promise.map with a concurrency option, allowing you to specify how many promises to run in parallel, which is particularly useful for resource-intensive tasks.

  • async:

    Async provides various functions that allow you to control the concurrency of asynchronous operations, such as async.parallelLimit and async.eachLimit, making it easy to manage how many tasks run simultaneously.

  • q:

    Q does not provide built-in concurrency control features, focusing instead on basic promise functionality. For concurrency control, additional logic would need to be implemented manually.

Error Handling

  • p-map:

    P-map allows you to handle errors in the mapping function, and if an error occurs, it will reject the promise, making it easier to manage errors in a concurrent mapping scenario.

  • bluebird:

    Bluebird enhances error handling with its promise chaining capabilities, allowing you to catch errors at any point in the promise chain using .catch(). It also supports Promise.try for wrapping synchronous code in a promise, making error handling more straightforward.

  • async:

    Async provides robust error handling capabilities through its callback-based approach, allowing you to handle errors at each step of the asynchronous flow, which can be particularly useful in complex workflows.

  • q:

    Q provides basic error handling through promise rejection, allowing you to catch errors using .catch(), but lacks the advanced error handling features found in other libraries.

Performance

  • p-map:

    P-map is lightweight and designed for performance when mapping over asynchronous operations, ensuring that it does not introduce significant overhead while managing concurrency.

  • bluebird:

    Bluebird is known for its high performance, particularly in promise-heavy applications. It is optimized for speed and can outperform native promises in many scenarios due to its efficient implementation.

  • async:

    Async is optimized for performance in managing asynchronous control flows, but its callback-based nature may introduce some overhead compared to promise-based libraries.

  • q:

    Q is relatively simple and performs adequately for basic promise functionality, but it may not match the performance optimizations found in more feature-rich libraries like Bluebird.

Learning Curve

  • p-map:

    P-map has a low learning curve, especially for developers familiar with the native Promise API, as it provides a straightforward method for mapping over asynchronous tasks.

  • bluebird:

    Bluebird has a relatively gentle learning curve for those already familiar with promises, as it extends the native Promise API with additional features that are easy to grasp.

  • async:

    Async has a moderate learning curve due to its callback-based API, which may require developers to familiarize themselves with its various functions and control flow patterns.

  • q:

    Q is easy to learn for beginners, as it offers a simple and intuitive API for working with promises, making it a good choice for those new to asynchronous programming.

Extensibility

  • p-map:

    P-map is focused on a specific use case (mapping with concurrency) and is not designed for extensibility beyond that, making it less flexible than the other libraries.

  • bluebird:

    Bluebird is also extensible, providing a range of utility methods that can be combined to create powerful asynchronous workflows, and it supports promisifying existing APIs easily.

  • async:

    Async is highly extensible, allowing developers to create custom control flow functions and integrate them into their workflows, making it suitable for complex applications.

  • q:

    Q is less extensible compared to others, as it primarily focuses on basic promise functionality without offering extensive utility methods or customization options.

How to Choose: p-map vs bluebird vs async vs q

  • p-map:

    Choose p-map if you need a lightweight library specifically designed for mapping over asynchronous operations with concurrency control. It allows you to limit the number of concurrent promises, making it ideal for scenarios where you want to avoid overwhelming resources while processing multiple asynchronous tasks.

  • bluebird:

    Choose Bluebird if you require a high-performance promise library with extensive features such as cancellation, progress tracking, and a variety of utility methods for working with promises. Bluebird is optimized for speed and can significantly improve performance in promise-heavy applications.

  • async:

    Choose Async if you need a versatile library that provides a rich set of functions for working with asynchronous JavaScript, including control flow functions like series, parallel, and waterfall. It is particularly useful for managing multiple asynchronous operations and offers a straightforward API for handling callbacks.

  • q:

    Choose Q if you are looking for a simple and easy-to-use promise library that provides a clean API for working with promises. It is particularly useful for projects that require basic promise functionality without the overhead of additional features.

Similar Npm Packages to p-map

p-map is a utility library for mapping over asynchronous operations in a more manageable way. It allows developers to run multiple promises concurrently while controlling the number of promises that are executed at any given time. This makes it particularly useful for scenarios where you need to perform multiple asynchronous tasks without overwhelming the system or the API being called. With p-map, you can specify a concurrency limit, ensuring that only a certain number of promises are processed simultaneously, which helps in optimizing resource usage and improving performance.

While p-map is a great tool for handling concurrent asynchronous operations, there are several alternatives that provide similar functionalities. Here are a few noteworthy alternatives:

  • p-all is a utility that allows you to run multiple promises in parallel and returns a single promise that resolves when all of the promises have resolved. Unlike p-map, which focuses on mapping over an array with concurrency control, p-all is straightforward and simply executes all promises at once. This can be useful when you want to wait for multiple asynchronous operations to complete without worrying about limiting the number of concurrent executions.

  • p-queue is a promise queue that allows you to manage the execution of asynchronous tasks with fine-grained control. It provides features such as concurrency limits, priority levels, and the ability to pause and resume the queue. p-queue is particularly useful when you need to manage a large number of asynchronous tasks and want to ensure that they are executed in a controlled manner, making it a powerful alternative to p-map for more complex scenarios.

  • p-series is a utility that runs promises in series, meaning that it waits for each promise to resolve before starting the next one. This is different from p-map, which allows for concurrent execution. If your use case requires that tasks be executed one after another rather than in parallel, p-series is the appropriate choice.

To explore how these packages compare, check out the following link: Comparing p-all vs p-map vs p-queue vs p-series.

Similar Npm Packages to bluebird

bluebird is a fully-featured promise library for JavaScript that provides a powerful and flexible way to work with asynchronous operations. It enhances the native JavaScript promises by adding a wide range of features, such as cancellation, progress reporting, and more robust error handling. Bluebird is particularly useful for developers who need to manage complex asynchronous workflows and want to take advantage of its performance optimizations.

While Bluebird is a popular choice for promise management, there are several alternatives available in the JavaScript ecosystem. Here are a few noteworthy options:

  • lie is a lightweight promise library that aims to provide a simple and minimalistic implementation of the Promise/A+ specification. It is designed for developers who need a straightforward promise solution without the additional features and overhead that come with larger libraries like Bluebird. Lie is particularly useful for smaller projects or when you want to keep your dependencies minimal.

  • q is another promise library that offers a rich set of features for managing asynchronous operations. It was one of the first libraries to implement the promise concept in JavaScript and provides a variety of utilities for working with promises, such as chaining, error handling, and more. Q is a good choice for developers who need a robust promise implementation with a focus on compatibility and performance.

  • rsvp is a promise library that was created to provide a simple and reliable implementation of promises for JavaScript. It includes features like promise chaining, error handling, and the ability to handle multiple promises concurrently. RSVP is particularly useful for developers who want a straightforward promise solution that is easy to use and integrates well with existing codebases.

  • when is a promise library that focuses on providing a powerful and flexible way to work with asynchronous operations. It offers features like chaining, error handling, and the ability to combine multiple promises. When is a great option for developers who need a comprehensive promise library that can handle complex asynchronous workflows.

To see how Bluebird compares with lie, q, rsvp, and when, check out the comparison: Comparing bluebird vs lie vs q vs rsvp vs when.

Similar Npm Packages to async

async is a utility module that provides powerful functions for working with asynchronous JavaScript. It simplifies the process of managing asynchronous operations, allowing developers to write cleaner and more maintainable code. With features like parallel execution, series execution, and control flow, async is particularly useful for handling complex asynchronous workflows. However, there are several alternatives in the JavaScript ecosystem that also provide similar functionalities. Here are a few notable ones:

  • bluebird is a fully-featured promise library that offers a wide range of utilities for working with promises. It enhances the native Promise functionality by providing additional features such as cancellation, progress tracking, and more robust error handling. bluebird is known for its performance and is a great choice for developers looking for an advanced promise library that can handle complex asynchronous tasks with ease.

  • p-map is a lightweight utility that allows you to map over an array asynchronously, executing a provided function for each element in parallel. It is particularly useful when you need to perform asynchronous operations on an array of items and want to control the concurrency level. p-map is simple to use and can be a great alternative for scenarios where you need to process multiple asynchronous tasks without the overhead of a larger library.

  • q is another promise library that focuses on providing a simple and straightforward API for working with asynchronous code. It was one of the earlier promise libraries in the JavaScript ecosystem and offers features like chaining, error handling, and more. While it may not be as feature-rich as some of the newer libraries, q is still a solid choice for developers looking for a lightweight solution for managing asynchronous operations.

To see how async compares with bluebird, p-map, and q, check out the comparison: Comparing async vs bluebird vs p-map vs q.

Similar Npm Packages to q

q is a popular promise library for JavaScript that provides a simple and powerful way to work with asynchronous code. It allows developers to create and manage promises, making it easier to handle asynchronous operations and avoid callback hell. While q offers robust promise management, there are several alternatives in the JavaScript ecosystem that also provide similar functionalities. Here are a few noteworthy alternatives:

  • async is a utility module that provides powerful functions for working with asynchronous JavaScript. It simplifies the process of managing asynchronous operations, providing a variety of control flow patterns such as series, parallel, and waterfall. If you need to handle multiple asynchronous tasks and want a comprehensive toolkit for managing their execution order, async is a solid choice. Its flexibility and extensive set of functions make it suitable for a wide range of scenarios, from simple callbacks to complex workflows.
  • bluebird is another popular promise library that extends the native JavaScript promise functionality. It offers a rich set of features, including advanced error handling, cancellation, and performance optimizations. bluebird is particularly useful for applications that require high-performance promise management and complex asynchronous workflows. If you are looking for a promise library that provides additional features and optimizations over native promises, bluebird is worth considering.
  • p-map is a lightweight promise utility that allows you to map over an array of items and return a promise for each item. It is particularly useful for performing asynchronous operations on arrays while controlling concurrency. If you need to process multiple asynchronous tasks concurrently and want to limit the number of promises running at the same time, p-map provides a simple and effective solution.

To explore how q compares with async, bluebird, and p-map, check out the comparison: Comparing async vs bluebird vs p-map vs q.

README for p-map

p-map

Map over promises concurrently

Useful when you need to run promise-returning & async functions multiple times with different inputs concurrently.

This is different from Promise.all() in that you can control the concurrency and also decide whether or not to stop iterating when there's an error.

Install

npm install p-map

Usage

import pMap from 'p-map';
import got from 'got';

const sites = [
	getWebsiteFromUsername('sindresorhus'), //=> Promise
	'https://avajs.dev',
	'https://github.com'
];

const mapper = async site => {
	const {requestUrl} = await got.head(site);
	return requestUrl;
};

const result = await pMap(sites, mapper, {concurrency: 2});

console.log(result);
//=> ['https://sindresorhus.com/', 'https://avajs.dev/', 'https://github.com/']

API

pMap(input, mapper, options?)

Returns a Promise that is fulfilled when all promises in input and ones returned from mapper are fulfilled, or rejects if any of the promises reject. The fulfilled value is an Array of the fulfilled values returned from mapper in input order.

pMapIterable(input, mapper, options?)

Returns an async iterable that streams each return value from mapper in order.

import {pMapIterable} from 'p-map';

// Multiple posts are fetched concurrently, with limited concurrency and backpressure
for await (const post of pMapIterable(postIds, getPostMetadata, {concurrency: 8})) {
	console.log(post);
};

input

Type: AsyncIterable<Promise<unknown> | unknown> | Iterable<Promise<unknown> | unknown>

Synchronous or asynchronous iterable that is iterated over concurrently, calling the mapper function for each element. Each iterated item is await'd before the mapper is invoked so the iterable may return a Promise that resolves to an item.

Asynchronous iterables (different from synchronous iterables that return Promise that resolves to an item) can be used when the next item may not be ready without waiting for an asynchronous process to complete and/or the end of the iterable may be reached after the asynchronous process completes. For example, reading from a remote queue when the queue has reached empty, or reading lines from a stream.

mapper(element, index)

Type: Function

Expected to return a Promise or value.

options

Type: object

concurrency

Type: number (Integer)
Default: Infinity
Minimum: 1

Number of concurrently pending promises returned by mapper.

backpressure

Only for pMapIterable

Type: number (Integer)
Default: options.concurrency
Minimum: options.concurrency

Maximum number of promises returned by mapper that have resolved but not yet collected by the consumer of the async iterable. Calls to mapper will be limited so that there is never too much backpressure.

Useful whenever you are consuming the iterable slower than what the mapper function can produce concurrently. For example, to avoid making an overwhelming number of HTTP requests if you are saving each of the results to a database.

stopOnError

Only for pMap

Type: boolean
Default: true

When true, the first mapper rejection will be rejected back to the consumer.

When false, instead of stopping when a promise rejects, it will wait for all the promises to settle and then reject with an AggregateError containing all the errors from the rejected promises.

Caveat: When true, any already-started async mappers will continue to run until they resolve or reject. In the case of infinite concurrency with sync iterables, all mappers are invoked on startup and will continue after the first rejection. Issue #51 can be implemented for abort control.

signal

Only for pMap

Type: AbortSignal

You can abort the promises using AbortController.

import pMap from 'p-map';
import delay from 'delay';

const abortController = new AbortController();

setTimeout(() => {
	abortController.abort();
}, 500);

const mapper = async value => value;

await pMap([delay(1000), delay(1000)], mapper, {signal: abortController.signal});
// Throws AbortError (DOMException) after 500 ms.

pMapSkip

Return this value from a mapper function to skip including the value in the returned array.

import pMap, {pMapSkip} from 'p-map';
import got from 'got';

const sites = [
	getWebsiteFromUsername('sindresorhus'), //=> Promise
	'https://avajs.dev',
	'https://example.invalid',
	'https://github.com'
];

const mapper = async site => {
	try {
		const {requestUrl} = await got.head(site);
		return requestUrl;
	} catch {
		return pMapSkip;
	}
};

const result = await pMap(sites, mapper, {concurrency: 2});

console.log(result);
//=> ['https://sindresorhus.com/', 'https://avajs.dev/', 'https://github.com/']

Related

  • p-all - Run promise-returning & async functions concurrently with optional limited concurrency
  • p-filter - Filter promises concurrently
  • p-times - Run promise-returning & async functions a specific number of times concurrently
  • p-props - Like Promise.all() but for Map and Object
  • p-map-series - Map over promises serially
  • More…
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