JavaScript > Promises

The why, what, and how. "A brief introduction [...] primarily aimed at frontend developers".

Chapter from You Don't Know JS: Async & Performance

An interactive nodeschool workshop

@sindresorhus's notes, patterns, and solutions to common Promise problems

Promise behaviour demonstrated and explained by common questions and their answers.

Promise behaviour demonstrated and explained by common questions and their answers.

Quick definitions of possible states.

Promise visualization playground for the adventurous.

Fully featured, extremely performant. Long stack traces & generator/coroutine support.

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

Lightweight with a few extras. Compatible down to IE6!

One of the original implementations. Long stack traces and other goodies.

Small with nodeify, denodify and done() additions.

Packed with control flow, functional, and utility methods.

Ponyfill. Node-oriented, but browserifyable. Extremely small implementation.

Polyfill. Browser and node-compatible.

Opt-in polyfill. A strict-spec subset of rsvp.js.

Small, browserifyable with an opt-in polyfill.

Use native, or fall back to pinkie. Great for node library authors.

Loads the first available implementation. Safe for browserify.

Delay a promise a specified amount of time.

Promisify ("denodify") a callback-style function.

Make unhandled promise rejections fail loudly instead of the default silent fail.

Make unhandled promise rejections fail hard right away instead of the default silent fail

Promise queue with concurrency control

Break out of a promise chain

Create a lazy promise that defers execution until ".then()" or ".catch()" is called

Create a deferred promise

Conditional promise chains

Tap into a promise chain without affecting its value or state

Map over promises concurrently

Run promise-returning & async functions concurrently with optional limited concurrency

Run multiple promise-returning & async functions with limited concurrency

Run promise-returning & async functions a specific number of times concurrently

Conditional promise catch handler

Measure the time a promise takes to resolve

Log the value/error of a promise

Filter promises concurrently

Settle promises concurrently and get their fulfillment value or rejection reason

Memoize promise-returning & async functions

Calls a function repeatedly while a condition returns true and then resolves the promise

Throttle promise-returning & async functions

Debounce promise-returning & async functions

Retry a promise-returning or async function

Wait for a condition to be true

Timeout a promise after a specified amount of time

A better Promise.race()

Promise#try() ponyfill - Starts a promise chain

Promise#finally() ponyfill - Invoked when the promise is settled regardless of outcome

Wait for any promise to be fulfilled

Wait for a specified number of promises to be fulfilled

Compose promise-returning & async functions into a reusable pipeline

Iterate over promises serially

Map over promises serially

Reduce a list of values using promises into a promise for a value

Like Promise.all() but for Map and Object

Standalone bluebird.method. Turn a synchronously-returning method into a promise-returning one.

Determine if something looks like a Promise.

Resolve when a stream ends. Optional buffering (be careful with this!)

Write async functions in a blocking style using promises and generators. Like bluebird.coroutine.

Like task.js and bluebird.coroutine, but supports thunks too.

Calls a function repeatedly until a condition returns true and then resolves the promise.

Calls a function repeatedly while a condition returns true and then resolves the promise.

Push a set of work to be done in a configurable serial fashion

Standalone nodeify method which calls a Node-style callback on resolution or rejection.