How to reset state in redux?

You need to write a root reducer in your application which delegate handling the action to the reducer generated by combineReducers(). For example, let us take rootReducer to return the initial state after USER_LOGOUT action. As we know, reducers are supposed to return the initial state when they are called with undefined as the first argument, no matter the action.

const appReducer = combineReducers({
  /* your app’s top-level reducers */
})

const rootReducer = (state, action) => {
  if (action.type === 'USER_LOGOUT') {
    state = undefined
  }

  return appReducer(state, action)
}

In case of using redux-persist, you may also need to clean your storage. Redux-perist keeps a copy of your state in a storage engine. First, you need to import the appropriate storage engine and then, to parse the state before setting it to undefined and clean each storage state key,

const appReducer = combineReducers({
  /* your app’s top-level reducers */
})

const rootReducer = (state, action) => {
  if (action.type === 'USER_LOGOUT') {
    Object.keys(state).forEach(key => {
                storage.removeItem(`persist:${key}`);
            });
            state = undefined;
  }

  return appReducer(state, action)
}