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".

Resources, Blogs, and Books

caniuse promises
Promise Cookbook The why, what, and how. "A brief introduction […] primarily aimed at frontend developers".
You’re Missing the Point of Promises @domenic shows that promises are much more than callback aggregation, and that jQuery’s implementation (prior to 3.0) isn’t enough.
JavaScript Promises: There and back again Basics of JavaScript’s native promise implementation.
Fates and States Quick definitions of possible states.
Promise anti-patterns Common misuses and how to avoid them.
JavaScript with Promises from O’Reilly. Short and to-the-point. Uses native and bluebird.

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.

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 (“denofify”) a callback-style function.
promise-every - Standalone bluebird.every. Execute one after the other sequentially.
promise-filter - Standalone bluebird.filter. Filter an array to a promise.
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.