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.