A redux middleware for @vkammerer/postmessage-raf.

This library makes it possible to pass FSA actions between two Redux stores (one in the main thread and one in a worker) in a declarative way.

It provides a "Ping mode", which optimizes the time at which messages are sent between the main and the worker threads, so that every message is exchanged at the beginning of a requestAnimationFrame call.

If you want to see it in action, see vkammerer/redux-postmessage-raf-examples, deployed at vkammerer.github.io/redux-postmessage-raf-examples/.

If you want to quickly try it yourself, you main find the boilerplate useful.

Installation

npm i @vkammerer/redux-postmessage-raf

Initialization

In the main thread:

import { createStore, applyMiddleware } from "redux";
import { createMainMiddleware } from "@vkammerer/redux-postmessage-raf";

export const slaveWorker = new Worker("./slave.js");
const mainMiddleware = createMainMiddleware({ worker: slaveWorker });

const store = createStore(reducer, applyMiddleware(mainMiddleware));

In "slave.js", the worker:

import { createStore, applyMiddleware } from "redux";
import { createWorkerMiddleware } from "@vkammerer/redux-postmessage-raf";

const workerMiddleware = createWorkerMiddleware();

const store = createStore(reducer, applyMiddleware(workerMiddleware));

Basic usage

An action will be passed to another thread store if the meta attribute toWorker or toMain is set to true.

In the main thread:

dispatch({
  type: 'UI_ACTION',
  meta: {
    toWorker: true, // This action will be passed to the worker store.
    ignoreSelf: true // This action will not be propagated to other middlewares in the main store
  }
});

In the worker:

dispatch({
  type: 'WORKER_ACTION',
  meta: {
    toMain: true, // This action will be passed to the main thread store.
    ignoreSelf: true // This action will not be propagated to other middlewares in the worker store
  }
});

Ping mode

The Ping mode can be started with the following action:
In the worker:

dispatch({
  type: 'PING_START',
  meta: {
    toMain: true
  }
});
// This action will start the ping mode.

And it can be stopped with the following action:
In the worker:

dispatch({
  type: 'PING_STOP',
  meta: {
    toMain: true
  }
});
// This action will stop the ping mode.

API

Ping mode actions

The main and worker middlewares can opt in, at initialization time, to dispatch actions for any hook in the message exchange lifecycle: beforePing, afterPing, beforePong and afterPong. For example, in the worker:

const workerMiddleware = createWorkerMiddleware({
  dispatchAfterPong: true,
  /*
    After each pong message is sent, an action with the following format will be dispatched:
    {
      type: "PONG_AFTER",
      payload: 10 // number of pongs since 'PING_START' was dispatched
    }
  */
});

Delayed actions

In ping mode, the worker can decide to delay the action to be dispatched to the main store by setting additional meta attributes:
In the worker:

dispatch({
  type: 'DELAYED_WORKER_ACTION',
  meta: {
    toMain: true,
    delay: {
      pingCount: 10,
      /*
        Registers the action to be dispatched in the main thread store
        at the 10th ping since 'START_PING' was dispatched.
        If the ping has already occured or if the pinging mode is stopped before,
        the action will be ignored.
        Not to be used in conjunction with 'index' here under
      */
      index: 12
      /*
        Registers the action to be dispatched 12 pings after the main thread receives it.
        If the pinging mode is stopped before, the action will be ignored.
        Not to be used in conjunction with 'count' here above
      */
    }
  }
});