Awesome Promises

A curated list of useful resources for JavaScript Promises

Inspired by the awesome list thing. Not to be confused with other awesome promises like "I promise you a million dollars" or "I promise you'll stay fit and never have to go to the gym again".

Table of Contents

• Resources, Blogs, and Books
• Promises/A+ Implementations (ES6/ES2015 compatible)
  • Strict Implementations
  • Implementations with extras
  • Fallbacks
• Convenience Utilities

Resources, Blogs, and Books

For beginners

• Promise Cookbook - The why, what, and how. "A brief introduction [...] primarily aimed at frontend developers".
• Promises for Asynchronous Programming - Chapter from Exploring ES6
• You Don't Know JS: Promises - Chapter from You Don't Know JS: Async & Performance
• JavaScript Promises: There and back again - Basics of JavaScript's native promise implementation.
• JavaScript with Promises - from O'Reilly. Short and to-the-point. Uses native and bluebird.
• Promise it won't hurt - An interactive nodeschool workshop
• ES6 Kata Promises - Promises Katas : Basics
• ES6 Promises in Depth

Deep Dive

• You're Missing the Point of Promises - Promises are much more than callback aggregation, and that jQuery's implementation (prior to 3.0) isn't enough.
• We have a problem with promises - "Many of us are using promises without really understanding them."
• Promise anti-patterns - Common misuses and how to avoid them.
• Promise anti-patterns (2) - Another set of promises anti-patterns
• Promise Ponderings, (Anti-)Patterns, and Apologies - Promise behaviour demonstrated and explained by common questions and their answers.
• Javascript Promises...In Wicked Detail - Recreate the promise implementation
• Writing Promise-Using Specifications - "This document gives guidance on how to write specifications that create, accept, or manipulate promises"

References

• Promises/A+ specification
• caniuse promises
• Fates and States - Quick definitions of possible states.
• Promisees - Promise visualization playground for the adventurous.

Promises/A+ Implementations (ES6/ES2015 compatible)

Strict Implementations

These implement no more or less than the es6 spec. They make great polyfills and are exceptionally compatible with native promises.

• pinkie - Ponyfill. Node-oriented, but browserifyable. Extremely small implementation.
• native-promise-only - Polyfill. Browser and node-compatible.
• es6-promise - Opt-in polyfill. A strict-spec subset of rsvp.js.
• lie - Small, browserifyable with an opt-in polyfill.

Implementations with extras

All of these provide more features than the language yet remain compatible. Node + Browsers for all.

• bluebird - Fully featured, extremely performant. Long stack traces & generator/coroutine support.
• rsvp.js - Lightweight with a few extras. Compatible down to IE6!
• Q - One of the original implementations. Long stack traces and other goodies.
• then/promise - Small with nodeify, denodify and done() additions.
• when.js - Packed with control flow, functional, and utility methods.

Fallbacks

• native-or-bluebird - Helps transition to completely native.
• pinkie-promise - Use native, or fall back to pinkie. Great for node library authors.
• any-promise - Loads the first available implementation. Safe for browserify.

Convenience Utilities

Native and strictly spec-compliant promises are awesome for compatibility, future-proofness, library authors, and browsers. However, libraries like bluebird patch goodies onto the Promise constructor and prototype. Solution? tiny modules of course!

• pify - Promisify ("denodify") a callback-style function.
• promise-each - Standalone bluebird.each. Execute one after the other sequentially.
• promise-filter - Standalone bluebird.filter. Filter an array to a promise.
• promise-finally - Standalone bluebird finally(). Execute a handler unconditionally after others have been handled.
• promise-map - Standalone bluebird.map. Map an array to a promise.
• promise-method - Standalone bluebird.method. Turn a synchronously-returning method into a promise-returning one.
• promise-props - Standalone implementation of bluebird's bluebird.props or rsvp's RSVP.hash
• promise-reduce - Standalone bluebird.reduce. Reduce an array to a promise.
• promise-some - Standalone bluebird.some. Check if an element passes the predicate, return a promise.
• promise-try - Standalone bluebird.try. Execute a synchronously-returning function and return a promise.
• is-promise - Determine if something looks like a Promise.
• sprom - Resolve when a stream ends. Optional buffering (be careful with this!)
• task.js - Write async functions in a blocking style using promises and generators. Like bluebird.coroutine.
• co - Like task.js and bluebird.coroutine, but supports thunks too.
• lie-fs - Promise wrappers for Node's FS API.
• immediate-promise - Returns a promise resolved in the next event loop - think setImmediate().
• delay - Delay a promise a specified amount of time.
• promise-whilst - Calls a function repeatedly if and while a condition returns true and then resolves the promise.
• loud-rejection - Make unhandled promise rejections fail loudly instead of the default silent fail.
• promise-until - Calls a function repeatedly if a condition returns false and until the condition returns true and then resolves the promise.
• promise-do-until - Calls a function repeatedly until a condition returns true and then resolves the promise.
• promise-do-whilst - Calls a function repeatedly while a condition returns true and then resolves the promise.
• promise-semaphore - Push a set of work to be done in a configurable serial fashion

License

Licensed under the Creative Commons CC0 License.