memoriser.js

export const shalowCompareArgs = (args, _args) => (
  _args == null ||
  args.length !== _args.length ||
  args.some((a, index) => a !== _args[index])
);

export const memorize = (func, compare = shalowCompareArgs) => {
  let _args;
  let _res;
  return (...args) => {
    if (compare(args, _args)) {
      _args = args;
      _res = func(..._args);
    }
    return _res;
  };
};

export const combineSelectors = (entrySelectors, selector, memorizer = memorize) => {
  if (typeof memorizer === 'function') selector = memorizer(selector);
  return (...args) => selector(...entrySelectors.map(apply(args)));
};

export const getUsers = combineSelectors(
  [getUserIds, getUserEntities], mapIds, memorize2
);

export const getUsers = combineSelectors([getUserIds, getUserEntities], mapIds);

memorize.js

export const memorize1 = f => ((_a, res) =>
  a => ( // eslint-disable-line no-return-assign
    _a !== a ? res = f(_a = a) : res
  )
)();

export const memorize2 = f => ((_a, _b, res) =>
  (a, b) => ( // eslint-disable-line no-return-assign
    _a !== a || _b !== b ? res = f(_a = a, _b = b) : res
  )
)();

export const memorize3 = f => ((_a, _b, _c, res) =>
  (a, b, c) => ( // eslint-disable-line no-return-assign
    _a !== a || _b !== b || _c !== c
      ? res = f(_a = a, _b = b, _c = c)
      : res
  )
)();

sample-1.state.js

state = {

  users: [
    { id: 1, ... },
    { id: 2, ... },
    { id: 3, ... },
    { id: 4, ... },
    ...
  ],

  modals: {
    succcess: false,
    error: false,
  },

  loading: false,

};

sample-2.state.js

state = {

  users: {
    allIds: [1, 2, 3, 4, ...],

    byId: {
      1: { id: 1, ... },
      2: { id: 2, ... },
      3: { id: 3, ... },
      4: { id: 4, ... },
    ...
  },

  modals: {
    succcess: false,
    error: false,
  },

  loading: false,

};

selectors.js

const apply = args => f => f(...args);

const shalowCompareArgs = (args, pArgs) => (
  args == null || pArgs == null ||
  args.length !== pArgs.length ||
  args.some((arg, index) => arg !== pArgs[index])
);

const memorizeDecorator = (f, compare = shalowCompareArgs) => (
  (_pArgs, _pRes) => (...args) => ( // eslint-disable-line no-return-assign
    _pRes = compare(args, _pArgs) ? f(...(_pArgs = args)) : _pRes
  )
)();

const createSelector = (memorize = memorizeDecorator) => (...selectors) => {
  const selector = memorize(selectors.pop());
  return (...args) => (
    selector(...selectors.map(apply(args)))
  );
};

const getIds = (state, props) => state.ids[props.listId] || [];
const getEntities = state => state.entities;
const byId = entities => id => entities[id];
const mapIds = (ids, entities) => ids.map(byId(entities));

const listSelector = ({ listId }) => ( // eslint-disable-line no-return-assign
  listSelector[listId] ||
  (listSelector[listId] = createSelector()(getIds, getEntities, mapIds))
);

const getAll = (state, props) => listSelector(props)(state, props);

sels.js

export const getUserEntities = state => state.users.byId;
export const getUserIds = state => state.users.allIds;
export const userById = state => id => state[id];
export const mapUserIds = memorize2(
  (ids, userEntities) => ids.map(userById(userEntities))
);

export const getUsers = state => mapUserIds(
  getUserIds(state), getUserEntities(state)
);
export const getUsersCount = state => getUserIds(state).length;

state-4.js

state = {

  users: {
    lists: {
      firstUserList: [1, 2, 3, 4, ...],
      secondUserList: [1, 2, 3, 4, ...],
    },

    byId: {
      1: { id: 1, ... },
      2: { id: 2, ... },
      3: { id: 3, ... },
      4: { id: 4, ... },
    ...
  },

  modals: {
    succcess: false,
    error: false,
  },

  loading: false,

};