@storybook/channels

What is @storybook/channels?

The @storybook/channels package is used within the Storybook ecosystem to facilitate communication between different parts of the Storybook environment, such as between the Storybook UI and the preview iframe where stories are rendered. It provides an event-driven channel that can be used for bidirectional communication.

What are @storybook/channels's main functionalities?

Creating a channel

This code sample demonstrates how to create a new channel using the @storybook/channels package. The 'transport' object would be an implementation of the transport layer that the channel will use to send and receive messages.

import Channel from '@storybook/channels';
const channel = new Channel({ transport });

Sending a message

This code sample shows how to send a message with an event name and associated data through the channel. Other parts of the application can listen for 'eventName' and react accordingly.

channel.emit('eventName', eventData);

Listening for a message

This code sample illustrates how to listen for messages on the channel. The 'eventHandler' function will be called with the event data whenever a message with 'eventName' is emitted.

channel.on('eventName', eventHandler);

Removing a listener

This code sample shows how to remove a previously added event listener from the channel. This is useful for cleanup and preventing memory leaks.

channel.removeListener('eventName', eventHandler);

Other packages similar to @storybook/channels

eventemitter3

EventEmitter3 is a high-performance event emitter. While it provides similar event-driven communication capabilities, it does not include a transport layer for communication between different environments like @storybook/channels does.

mitt

Mitt is a tiny functional event emitter / pubsub. It offers similar event handling functionality but lacks the built-in transport layer for cross-environment communication that @storybook/channels provides.

README

Storybook Channel

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Storybook Channel is similar to an EventEmitter. Channels are used with Storybook implementations to send/receive events between the Storybook Manager and the Storybook Renderer.

class Channel {
  addListener(type, listener) {}
  addPeerListener(type, listener) {} // ignore events from itself
  emit(type, ...args) {}
  eventNames() {}
  listenerCount(type) {}
  listeners(type) {}
  on(type, listener) {}
  once(type, listener) {}
  prependListener(type, listener) {}
  prependOnceListener(type, listener) {}
  removeAllListeners(type) {}
  removeListener(type, listener) {}
}

The channel takes a Transport object as a parameter which will be used to send/receive messages. The transport object should implement this interface.

class Transport {
  send(event) {}
  setHandler(handler) {}
}

Currently, channels are baked into storybook implementations and therefore this module is not designed to be used directly by addon developers. When developing addons, use the getChannel method exported by @storybook/addons module. For this to work, Storybook implementations should use the setChannel method before loading addons.

import addons from '@storybook/addons';

const channel = addons.getChannel();

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For more information visit: storybook.js.org