Example Promises/A+ implementation. Simple, tiny, fast, fully async
Avow is a tiny, fast, fully asynchronous Promises/A+ implementation, and passes the Promises/A+ Test Suite. It tracks Promises/A+ and is currently forward compatible to the upcoming revision Promises/A+ (likely to be versioned 1.1.0).
It's around 150 lines of JS (sans comments, module boilerplate, and nextTick sniffing), under 650 bytes when closured+gzipped, supports unhandled rejection hooks for debugging, and is very fast in environments where a fast
nextTick is available. It uses
setImmediate if available (you can use NobleJS's setImmediate polyfill), and will fall back to
setTimeout (srsly, use the polyfill) otherwise.
I wrote avow as a stripped-down test bed for new ideas for when.js, cujo.js's full-featured promise implementation. I also hope that it serves as a simple example implementation for others who might want to implement promises either as a learning exercise, or as a part of a project/library/framework.
Yes, but you shouldn't. You should try when.js instead. It is even faster and provides many more features, like dealing with collections of promises, competitive races, and timed promises.
Again, probably not. I have no plans to support it in any way. I'll probably change the API without warning like I did from 1.0.0 to 2.0.0. You're on your own.
Download it, clone it, or
npm install avow
var avow = require'avow';// Create a promisevar promise = avow// ... do some work ...// Resolve the returned promise with a value, another promise,// or any well-behaved thenable.resolvevalue;// resolve(anotherPromise);// resolve(thenable);// Or reject itrejectreason;;// Create a fulfilled promisepromise = avowliftnonPromiseValue;// Create a promise whose fate follows another promisepromise = avowliftanotherPromise;// Attempt to assimilate and follow a well-behaved thenable's fatepromise = avowliftthenable;// Create a rejected promise that will usepromise = avowrejectedreason;
You can make your own custom configured instance of avow:
var myAvow = require'avow'constructoptions;
options is an object that can have any of the following properties:
enqueue- specify your own nextTick function
unhandled- callback to be notified when a promise becomes rejected, but has no rejection handler.
handled- callback to be notified if, at some point, a previously unhandled rejected promise become handled. Since promises are temporal, this can happen if a consumer adds a rejection handler using
then()at some point after the promise has been rejected.
protect- function that is called on every promise avow creates, to give you a chance to protect it, e.g. by supplying Object.freeze() here.
MIT License, Copyright (c) 2012-2013 Brian Cavalier