redux-loop/src/loop.js

Sequence your effects naturally and purely by returning them from your reducers.

import { throwInvariant } from './utils';
import Cmd, { isCmd } from './cmd';

export const isLoop = (array) => {
  return (
    Array.isArray(array) &&
    array.length === 2 &&
    isCmd(array[1]) &&
    !isCmd(array[0])
  );
};

export const getCmd = (loop) => {
  return isLoop(loop) ? loop[1] : null;
};

export const getModel = (loop) => {
  return isLoop(loop) ? loop[0] : loop;
};

export const loop = (model, cmd) => {
  if (process.env.NODE_ENV === 'development') {
    throwInvariant(isCmd(cmd), 'Given cmd is not an Cmd instance.');
  }

  return [model, cmd];
};

export const liftState = (state) => {
  return isLoop(state) ? state : loop(state, Cmd.none);
};