javascript - React redux logic done in parent reducer vs. child reducer -

in react redux doc todo example, dan passes action type toggle_todo todos passes on each individual todo. notice logic checking todo.id in todo reducer. couldn't logic have been done in todos well? me, seem better take care of logic @ higher level iterating through each todo rather passing work every todo , having them figure out if need toggle or now. there reason why dan did way?

const todo = (state = {}, action) => {   switch (action.type) {     case 'add_todo':       return {         id: action.id,         text: action.text,         completed: false       }     case 'toggle_todo':       if (state.id !== action.id) {         return state       }        return object.assign({}, state, {         completed: !state.completed       })      default:       return state   } }  const todos = (state = [], action) => {   switch (action.type) {     case 'add_todo':       return [         ...state,         todo(undefined, action)       ]     case 'toggle_todo':       return state.map(t =>         todo(t, action)       )     default:       return state   } }  export default todos 

i think right, if take @ todomvc example redux source code repository, you'll see 1 todos reducer.

the docs may bit outdated or such nested reducers may example of possibilities.