Pros of es6-promise

• More comprehensive implementation of the ES6 Promise specification
• Better support for advanced Promise features like Promise.race() and Promise.all()
• Larger community and more frequent updates

Cons of es6-promise

• Larger file size, which may impact performance in some applications
• More complex codebase, potentially making it harder to debug or customize
• Slightly steeper learning curve for developers new to Promises

Code Comparison

es6-promise:

var Promise = require('es6-promise').Promise;

var promise = new Promise(function(resolve, reject) {
  // Async operation here
  if (/* operation successful */) {
    resolve('Success!');
  } else {
    reject('Failure!');
  }
});

promise-polyfill:

var Promise = require('promise-polyfill').default;

var promise = new Promise(function(resolve, reject) {
  // Async operation here
  if (/* operation successful */) {
    resolve('Success!');
  } else {
    reject('Failure!');
  }
});

Both libraries provide similar basic Promise functionality, but es6-promise offers a more complete implementation of the ES6 specification. promise-polyfill is lighter and simpler, which may be preferable for projects with basic Promise needs or size constraints.

Pros of Bluebird

• Offers more advanced features and utilities beyond the standard Promise API
• Generally provides better performance, especially in older browsers
• Has extensive documentation and a large community

Cons of Bluebird

• Larger file size, which may impact load times and bundle sizes
• Steeper learning curve due to additional features and complexity
• Less frequently updated in recent years

Code Comparison

Promise-polyfill:

var promise = new Promise(function(resolve, reject) {
  setTimeout(function() {
    resolve('Success!');
  }, 1000);
});

Bluebird:

var Promise = require('bluebird');
var promise = new Promise(function(resolve, reject) {
  setTimeout(function() {
    resolve('Success!');
  }, 1000);
});

The basic usage is similar, but Bluebird offers additional methods and utilities:

Promise.map(items, function(item) {
  return processItem(item);
}).then(function(results) {
  console.log(results);
});

Promise-polyfill focuses on providing a lightweight polyfill for native Promises, while Bluebird offers a more feature-rich alternative with performance optimizations. Choose Promise-polyfill for simple Promise support in older environments, and Bluebird for advanced features and optimizations in larger applications.

Pros of Q

• More comprehensive feature set, including advanced functionality like progress tracking and cancellation
• Well-established and battle-tested in production environments
• Extensive documentation and community support

Cons of Q

• Larger file size and potentially higher performance overhead
• More complex API, which may be overkill for simpler use cases
• Less actively maintained in recent years

Code Comparison

Q:

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

promise-polyfill:

Promise.resolve(10)
.then(function (result) {
    console.log(result);
});

Summary

Q is a more feature-rich and mature library, offering advanced functionality beyond basic promises. However, promise-polyfill provides a lightweight alternative that closely mimics the native Promise API, making it a better choice for simple use cases or when bundle size is a concern. Q's syntax is slightly more verbose, while promise-polyfill adheres closely to the standard Promise syntax. Consider your project's specific needs when choosing between these libraries.

Pros of RSVP.js

• More comprehensive API with additional features like RSVP.hash and RSVP.filter
• Better suited for larger applications with complex asynchronous operations
• Actively maintained with regular updates and improvements

Cons of RSVP.js

• Larger file size, which may impact performance in smaller projects
• Steeper learning curve due to additional features and complexity
• May be overkill for simple projects that only require basic Promise functionality

Code Comparison

RSVP.js:

import RSVP from 'rsvp';

RSVP.resolve('Success').then(function(value) {
  console.log(value);
});

promise-polyfill:

import Promise from 'promise-polyfill';

Promise.resolve('Success').then(function(value) {
  console.log(value);
});

Both libraries provide similar basic Promise functionality, but RSVP.js offers additional methods and features for more complex scenarios. The choice between the two depends on the project's specific requirements, with promise-polyfill being more suitable for smaller projects or when a lightweight solution is needed, while RSVP.js is better for larger applications with more complex asynchronous operations.