handoff

handoff.js

PubSub with Promises.

handoff.js lets you do request/response with PubSub, using Promises.

let handoff = require('handoff');

handoff.subscribe('something', (n, message) => {
    return new Promise((resolve, reject) => setTimeout(() => resolve('received!'), 1000));
});

handoff.publish('something', 'hello!')
    .then(response =>  console.log(response)); // 'received!'

publish() returns a Promise which will be resolved at the end of a subscriber chain. Subscibers can return values or promises.

handoff.subscribe()

• name String (required)
• callback Function (required)
• priority Number (optional)

callback will receive 1 + N arguments. The first arg will be a Notification instance, the rest will be passed in exactly in the order the publisher published them in.

priority can be useful if you have multiple subscribers, the lower the priority the sooner in the chain a subscriber will receive the notification.

handoff.publish()

• name String (required)
• ...data * (optional)

...data (any args passed in after name) will be passed to all subscribers in order.

Notifications

Each time a subsciber's listener is invoked it receives a Notification instance as the first argument. You can think of this much like an Event object.

Notifications have a name property you can use to get the name of the notification that was sent; this is useful if you have a single callback for multiple subscribers.

Notifications also have a cancel() method. This is much like stopPropagation() for events. When you call cancel() any subscribers later in the chain will not hear about that notification, and the publishers Promise will be resolved or rejected by the current subscriber.

handoff.subscribe('something', (n, message) => {

    n.cancel(); // No other subscribers will hear about this notification.

    return new Promise((resolve, reject) => {

        setTimeout(() => {
            resolve('received!'); // Publisher's `then()` method will be invoked now.
        }, 1000);
    });
});

Rejections

Handoff will reject a promise in two instances :

• A subscriber cancelled the Notification. In these cases the Error object passed to the rejection handler will have a code property with a value of ECANCELED.

• There are no subscribers for a notification. In these cases the Error object passed to the rejection handler will have a code property with a value of ENOSYS.

License

This software is released under the terms of the MIT License.

(c) 2016 Taka Kojima (the "Author").
All Rights Reserved.

Permission is hereby granted, free of charge, to any person
obtaining a copy of this software and associated documentation
files (the "Software"), to deal in the Software without
restriction, including without limitation the rights to use,
copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the
Software is furnished to do so, subject to the following
conditions:

The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.

Distributions of all or part of the Software intended to be used
by the recipients as they would use the unmodified Software,
containing modifications that substantially alter, remove, or
disable functionality of the Software, outside of the documented
configuration mechanisms provided by the Software, shall be
modified such that the Author's bug reporting email addresses and
urls are either replaced with the contact information of the
parties responsible for the changes, or removed entirely.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
OTHER DEALINGS IN THE SOFTWARE.

Except where noted, this license applies to any and all software
programs and associated documentation files created by the
Author, when distributed with the Software.