// ... prev. code ommited
  
export const combineReducer = (reducers) => {
    const globalState = {};
    
    for (const [key, value] of Object.entries(reducers)) {
        // check it its a reducer
        if (typeof value === 'function') {
            globalState[key] = value(undefined, { type: '__@@PLACEHOLDER_ACTION__' });
        } else {
            // let the developer know the value is not a reducer
            console.error(`${value} is not a function`);
        }
    }
}