Redux with example: Share state between two reducers https://thesabbir.com/redux-with-example-share-state-between-two-reducers

ChatActionCreators.js

// using redux thunk async action
export function initiateNewChat(id, message) {
    return (dispatch, getState) => {
        // get friend from friends store
        const friend = getState()
            .friends[id];
        if (friend) {
            // if friend exists we initiate new chat
            return {
                type: 'INITIATE_CHAT',
                friend,
                message
            };
        }
        // if not we return a error action
        return {
            type: 'ERROR_CREATING_CHATBOX',
        }
    };
}

ChatBoxReducer.js

// state = chatoboxes
export function chatBoxReducer(state = {}, action) {
    switch (action.type) {
        case 'INITIATE_CHAT':
            // We have friends data with action.friend
            return state;
        default:
            return state;
    }
}