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Awesome Promises Awesome

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

For beginners

Deep Dive

References

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.
  • creed - Hyper performant & full featured like Bluebird, but FP-oriented. Coroutines, generators, promises, ES2015 iterables, & fantasy-land spec.
  • 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!

sindresorhus's many Promise utilities (see notes)

  • delay - Delay a promise a specified amount of time.
  • pify - Promisify ("denodify") a callback-style function.
  • loud-rejection - Make unhandled promise rejections fail loudly instead of the default silent fail.
  • hard-rejection - Make unhandled promise rejections fail hard right away instead of the default silent fail
  • p-queue - Promise queue with concurrency control
  • p-break - Break out of a promise chain
  • p-lazy - Create a lazy promise that defers execution until .then() or .catch() is called
  • p-defer - Create a deferred promise
  • p-if - Conditional promise chains
  • p-tap - Tap into a promise chain without affecting its value or state
  • p-map - Map over promises concurrently
  • p-all - Run promise-returning & async functions concurrently with optional limited concurrency
  • p-limit - Run multiple promise-returning & async functions with limited concurrency
  • p-times - Run promise-returning & async functions a specific number of times concurrently
  • p-catch-if - Conditional promise catch handler
  • p-time - Measure the time a promise takes to resolve
  • p-log - Log the value/error of a promise
  • p-filter - Filter promises concurrently
  • p-settle - Settle promises concurrently and get their fulfillment value or rejection reason
  • p-memoize - Memoize promise-returning & async functions
  • p-whilst - Calls a function repeatedly while a condition returns true and then resolves the promise
  • p-throttle - Throttle promise-returning & async functions
  • p-debounce - Debounce promise-returning & async functions
  • p-retry - Retry a promise-returning or async function
  • p-wait-for - Wait for a condition to be true
  • p-timeout - Timeout a promise after a specified amount of time
  • p-race - A better Promise.race()
  • p-try - Promise#try() ponyfill - Starts a promise chain
  • p-finally - Promise#finally() ponyfill - Invoked when the promise is settled regardless of outcome
  • p-any - Wait for any promise to be fulfilled
  • p-some - Wait for a specified number of promises to be fulfilled
  • p-pipe - Compose promise-returning & async functions into a reusable pipeline
  • p-each-series - Iterate over promises serially
  • p-map-series - Map over promises serially
  • p-reduce - Reduce a list of values using promises into a promise for a value
  • p-props - Like Promise.all() but for Map and Object

Others

  • promise-method - Standalone bluebird.method. Turn a synchronously-returning method into a promise-returning one.
  • 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.
  • 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
  • promise-nodeify - Standalone nodeify method which calls a Node-style callback on resolution or rejection.

License

Licensed under the Creative Commons CC0 License.