A Redux-like Flux implementation in <75 lines of code

flux.js

/**
 * Basic proof of concept.
 * - Hot reloadable
 * - Stateless stores
 * - Stores and action creators interoperable with Redux.
 */

import React, { Component } from 'react';

export default function dispatch(store, atom, action) {
  return store(atom, action);
}

export class Dispatcher extends Component {
  static propTypes = {
    store: React.PropTypes.func.isRequired
  };

  static childContextTypes = {
    dispatch: React.PropTypes.func,
    atom: React.PropTypes.any
  };

  getChildContext() {
    return {
      atom: this.state.atom,
      dispatch: this.dispatch.bind(this)
    };
  }

  constructor(props, context) {
    super(props, context);

    this.state = { atom: dispatch(props.store, undefined, {}) };
  }

  dispatch(payload) {
    this.setState(prevState => ({
      atom: dispatch(this.props.store, prevState.atom, payload)
    }));
  }

  render() {
    return typeof this.props.children === 'function'
      ? this.props.children(this.state.atom)
      : this.props.children;
  }
}

export class Injector extends Component {
  static contextTypes = {
    dispatch: React.PropTypes.func.isRequired,
    atom: React.PropTypes.any
  };

  static propTypes = {
    actions: React.PropTypes.object
  };

  performAction(actionCreator, ...args) {
    const { dispatch } = this.context;
    const payload = actionCreator(...args);

    return typeof payload === 'function'
      ? payload(dispatch)
      : dispatch(payload);
  };

  render() {
    const { dispatch, atom } = this.context;
    const { actions: _actions } = this.props;

    const actions = Object.keys(_actions).reduce((result, key) => {
      result[key] = this.performAction.bind(this, _actions[key]);
      return result;
    }, {});

    return this.props.children({ actions, atom });
  }
}

index.js

/**
 * Example usage
 * 
 * Based on Redux's counter example
 * https://github.com/gaearon/redux/tree/master/examples/counter
 */

import React, { Component, PropTypes } from 'react';
import { Dispatcher, Injector } from '../';

const INCREMENT_COUNTER = 'INCREMENT_COUNTER';
const DECREMENT_COUNTER = 'DECREMENT_COUNTER';

function counterStore(counter = 0, action) {
  switch (action.type) {
  case INCREMENT_COUNTER:
    return counter + 1;
  case DECREMENT_COUNTER:
    return counter - 10;
  default:
    return counter;
  }
}

function increment() {
  return {
    type: INCREMENT_COUNTER
  };
}

function decrement() {
  return {
    type: DECREMENT_COUNTER
  };
}

export default class CounterApp {
  render() {
    return (
      <Dispatcher
        // Instead of specifying an object of keys mapped to stores, just use a
        // higher-order store!
        store={(state = {}, action) => ({
          counter: counterStore(state.counter, action)
        })}
      >
        {() => (
          <Injector actions={{ increment, decrement }}>
            {({ actions, atom }) => (
              <Counter
                increment={actions.increment}
                decrement={actions.decrement}
                counter={atom.counter}
              />
            )}
          </Injector>
        )}
      </Dispatcher>
    );
  }
}

class Counter {
  static propTypes = {
    increment: PropTypes.func.isRequired,
    decrement: PropTypes.func.isRequired,
    counter: PropTypes.number.isRequired
  };

  render() {
    const { increment, decrement, counter } = this.props;

    return (
      <p>
        Clicked: {counter} times
        {' '}
        <button onClick={increment}>+</button>
        {' '}
        <button onClick={decrement}>-</button>
      </p>
    );
  }
}

@gaearon @acdlite
This is a draft and not completed:
demo: https://codesandbox.io/s/atomic-redux-q9prt

Atomic Redux:

import createAtom from "./atomic-redux";

const incomeAtom = createAtom({
  initialState: 0,
  actions: {
    change: (state, payload) => payload
  }
});

const taxAtom = createAtom({
  initialState: 0.1,
  subscribes: [incomeAtom],
  so: (income) => {
    if (income < 1000) return 0.1;
    if (income < 2000) return 0.15;
    if (income < 3000) return 0.2;
    if (income < 4000) return 0.25;
    return 0.3;
  }
});

export default function App() {
  const [income, incomeActions] = incomeAtom.useHook();
  const [tax] = taxAtom.useHook();

  const handleChange = (event) => incomeActions.change(event.target.value);

  return (
    <div>
      <input value={income} onChange={handleChange} />
      <br />
      Your Income is: {income}
      <br />
      Your Tax is: {tax}
      <br />
    </div>
  );
}

And inside /atomic-redux.js

import { useEffect, useState } from "react";
import { createStore } from "redux";

const PRIVATE_UPDATER = Symbol("PRIVATE_UPDATER");
const noop = () => {};

function createAtom({
  initialState,
  actions = {},
  subscribes = [],
  so = noop
}) {
  actions[PRIVATE_UPDATER] = (_, payload) => payload;

  let {
    getState,
    dispatch,
    subscribe
  } = createStore((state = initialState, { type, payload }) =>
    (actions[type] || (() => state))(state, payload)
  );

  subscribes.forEach((atom) =>
    atom.subscriber({
      dispatch,
      so
    })
  );

  const useHook = () => {
    const [state, setState] = useState(getState());
    useEffect(() => {
      const unsubscribe = subscribe(() => setState(getState()));
      return unsubscribe;
    }, []);
    return [
      state,
      Object.keys(actions).reduce(
        (acc, action) => ({
          ...acc,
          [action]: (payload) => dispatch({ type: action, payload })
        }),
        {}
      )
    ];
  };

  const subscriber = ({ dispatch, so }) =>
    subscribe(() =>
      dispatch({ type: PRIVATE_UPDATER, payload: so(getState()) })
    );

  return { useHook, subscriber };
}

export default createAtom;