Redux-lens.js

const stateIdLens = propLens('id')
const stateTokenLens = propLens('token')

let setCurrentUserId = (state, action) => set(idLens, action.payload.result, state)
let setCurrentUserToken = (state, action) => set(tokenLens, action.payload.token, state)
compose(setCurrentUserId, setCurrentUserToken)



const actionResultLens = propsLens('payload', 'result')
const actionTokenLens = propsLens('payload', 'token')

// set :: Lens a -> Lens a -> State -> Action -> State
const setState = (stateLens, actionLens) =>
  (state, action) => set(stateLens, view(actionLens, action), state)

const overState = (stateLens, actionLens, f) =>
  (state, action) => over(stateLens, f(view(actionLens, action), view(stateLens, state)), state)

const setCurrentUserId = setState(stateIdLens, actionResultLens)
const setCurrentUserToken = setState(stateTokenLens, actionTokenLens)


const reducer = createReducer(initialState, {
  [UPDATE]: compose(setCurrentUserId, setCurrentUserToken)
})



const countL = propLens('count')
const valueL = propsLens('payload', 'value')


const setCount = setState(countL, valueL)
const increment = overState(countL, valueL, (count, value) => count + value)

// or with a simplyer overState
const increment = ({ payload: { value } }) => overState(countL, (count) => count + value)
const increment = action => overState(countL, (count) => count + action.payload.value)