combine-reducers.js

// Straight from documentation.
const reducer = combineReducers({
  a: doSomethingWithA,
  b: processB,
  c: c
});

// This is functionally equivalent.
function reducer(state, action) {
  return {
    a: doSomethingWithA(state.a, action),
    b: processB(state.b, action),
    c: c(state.c, action)
  };
}

// Simple change to pass the entire state to each reducer.
// You have to be extra careful to keep state immutable here.
function reducer(state, action) {
  return {
    a: doSomethingWithA(state.a, action, state),
    b: processB(state.b, action, state),
    c: c(state.c, action, state)
  };
}