Promise

Implementation of javascript Promise/A+ standard, plus .finally and onUnhandledRejection.

Nothing more. Clean and tiny (3.9 KB Only, or 1.4 KB gzipped).

Use it by: npm install beauty-promise, or include browser-bundles/promise.min.js.

• Why not bluebird? -- Too large
• Why not babel (core-js) runtime -- Too large (and simple)
• Why not q -- Still too large
• Why not then@promise -- Well, it's not quite large (although still larger than this one). But I don't feel good for its implementation of 'unhandled rejection tracking' - complex api, and the trigger is delayed.

What I want is a basic and tiny Promise, with useful 'unhandled rejection tracking' (which is only supported on Chrome for native Promise). So I created this one.

Promise API

It is supposed to be implemented with the same behavior with nodejs/browser native Promise. Test cases covered.

Constructor

new Promise(fn: function(resolve, reject))

Promise Instance Methods

promise.then(onFulfilled: null|function(value), onRejected: null|function(reason))

promise.catch(onRejected: function(reason))

promise.finally(onRejected: function(valueOrReason))

Static Methods

Promise.resolve(value: *)

Promise.reject(reason: *)

Promise.all(promises: Array.<Promise | Thenable>)

Promise.race(promises: Array.<Promise | Thenable>)

Unhandled Promise Rejection

Promise.onUnhandledRejection = function (reason) {
    // ... handle your unhandled rejection
};