Pros of Bluebird

• Higher performance and faster execution compared to PromiseKit
• More extensive feature set, including advanced utilities like Promise.map and Promise.reduce
• Better cross-platform support, especially for older browsers and Node.js versions

Cons of Bluebird

• Larger library size, which may impact load times in browser environments
• Steeper learning curve due to its extensive API and advanced features
• Less native integration with Swift and iOS development compared to PromiseKit

Code Comparison

PromiseKit:

firstly {
    fetchUser()
}.then { user in
    fetchAvatar(user)
}.done { avatar in
    self.imageView.image = avatar
}.catch { error in
    print("Error: \(error)")
}

Bluebird:

Promise.resolve()
  .then(fetchUser)
  .then(fetchAvatar)
  .then(avatar => {
    imageView.src = avatar;
  })
  .catch(error => {
    console.error("Error:", error);
  });

Both libraries provide similar syntax for chaining promises, but PromiseKit's syntax is more Swift-oriented, while Bluebird follows a more traditional JavaScript promise pattern. PromiseKit uses firstly and done for better readability, while Bluebird relies on standard promise methods like then and catch.

Pros of Q

• More mature and widely adopted in the JavaScript ecosystem
• Supports a broader range of platforms, including older browsers
• Offers more advanced features like progress tracking and cancellation

Cons of Q

• Larger file size, which may impact performance in some applications
• Less actively maintained compared to PromiseKit
• Steeper learning curve for beginners due to its extensive API

Code Comparison

Q:

Q.fcall(function () {
    return 10;
})
.then(function (result) {
    console.log(result);
});

PromiseKit:

firstly {
    return 10
}.then { result in
    print(result)
}

Both libraries provide similar functionality for creating and chaining promises. Q uses a more JavaScript-centric approach, while PromiseKit is tailored for Swift and iOS development. PromiseKit's syntax is generally more concise and Swift-like, making it easier for iOS developers to integrate into their projects.

PromiseKit is actively maintained and optimized for iOS development, offering better integration with Apple's frameworks. It also provides a more lightweight solution, which can be beneficial for mobile applications where performance is crucial.

Q, on the other hand, offers a more comprehensive set of features and is better suited for complex asynchronous operations in JavaScript environments. Its wider adoption in the JavaScript community means more resources and third-party integrations are available.

Pros of Promise

• Lightweight and minimalistic implementation
• Focuses solely on Promise functionality without extra features
• Easy to integrate into existing projects due to its simplicity

Cons of Promise

• Less comprehensive feature set compared to PromiseKit
• Fewer utility functions and extensions
• May require additional libraries for more advanced use cases

Code Comparison

PromiseKit:

firstly {
    fetchUser()
}.then { user in
    fetchAvatar(user)
}.done { avatar in
    self.imageView.image = avatar
}.catch { error in
    self.show(error)
}

Promise:

fetchUser()
  .then(user => fetchAvatar(user))
  .then(avatar => {
    this.imageView.image = avatar;
  })
  .catch(error => {
    this.show(error);
  });

Summary

PromiseKit offers a more comprehensive solution with additional features and utilities, making it suitable for larger projects with complex asynchronous operations. Promise, on the other hand, provides a simpler and more lightweight implementation, focusing on core Promise functionality. PromiseKit's syntax is more Swift-oriented, while Promise follows a more traditional JavaScript-style approach. The choice between the two depends on the specific project requirements, language preferences, and the desired level of abstraction and feature set.

Pros of RSVP.js

• Lightweight and focused solely on Promises, making it more suitable for projects that don't require a full-featured library
• Better compatibility with older browsers, including IE8+
• More active development and frequent updates

Cons of RSVP.js

• Less extensive feature set compared to PromiseKit's comprehensive offerings
• Lacks some of the convenience methods and extensions provided by PromiseKit
• May require additional libraries or plugins for more advanced use cases

Code Comparison

RSVP.js:

RSVP.Promise.resolve(1)
  .then(value => value + 1)
  .then(value => console.log(value));

PromiseKit:

firstly {
    Promise.value(1)
}.map {
    $0 + 1
}.done {
    print($0)
}

Both libraries provide similar basic Promise functionality, but PromiseKit offers a more expressive and Swift-oriented syntax. RSVP.js follows a more traditional JavaScript Promise pattern, while PromiseKit leverages Swift's language features for a more idiomatic approach.

RSVP.js is better suited for JavaScript projects requiring broad browser support and a lightweight Promise implementation. PromiseKit, on the other hand, excels in Swift and Objective-C environments, offering a richer set of features and tighter integration with Apple's ecosystems.

Pros of async

• More mature and widely adopted in the Node.js ecosystem
• Supports a broader range of flow control patterns (e.g., parallel, series, waterfall)
• Lightweight and focused on asynchronous operations

Cons of async

• Limited to JavaScript/Node.js environments
• Callback-based approach can lead to callback hell in complex scenarios
• Lacks some modern features like cancellation and progress tracking

Code Comparison

async:

async.waterfall([
    function(callback) {
        callback(null, 'one', 'two');
    },
    function(arg1, arg2, callback) {
        callback(null, 'three');
    }
], function (err, result) {
    console.log(result);
});

PromiseKit:

firstly {
    fetch(url)
}.then { data in
    parse(data)
}.done { result in
    print(result)
}.catch { error in
    print(error)
}

Summary

async is a popular choice for Node.js developers, offering a wide range of flow control patterns and a lightweight approach to handling asynchronous operations. However, it's limited to JavaScript environments and can lead to callback hell in complex scenarios.

PromiseKit, on the other hand, provides a more modern promise-based approach with support for multiple languages and advanced features like cancellation. It offers a cleaner syntax for handling asynchronous operations but may have a steeper learning curve for developers new to promises.