reading-notes

Class Thirty-Seven Notes (401)

Because there may be multiple states to be updated and multiple events take place
combineReducers can be used to combine multiple reducers, where the default values are set in the reducer state arguement
A state can be managed as an immutable object by two ways:

newState = {…state}; return newState

state = {…state, property: action.payload} //desctructure the state object, and only alter the property of interest in that action

combineReducer() is a utility function to simplify the most common use case when writing Redux Reducers.
To assemble a new state tree, combineReducers() first call each slice reducer with its current slice of the state and the current action, and give the slice a chance to respond to the state if needed. So all reducers to get called when combineReducers() is used.
To define initial state in an app, a store must be created using createStore which takes in the preoadedState. This initialize the setore with state that was previously presisted elsewhere in the app or browser’s localstorage.

As an app grows more complex, each reducing function should be separated into its own function to manage states independently.
The combineReducer helper function turns an object whose values are different reducing functions into a single reducing function you can pass to createStore.
When naming reducers, a popular convention is to name reducers after the state slices they manage. So the developer can use the ES6 shorthand where combineReducers({ counter, todos }) is equivalent to combineReducers({ counter: counter, todos: todos })