FAQ: Strategies for Complex State - Reducer Composition

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This community-built FAQ covers the “Reducer Composition” exercise from the lesson “Strategies for Complex State”.

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This exercise can be found in the following Codecademy content:

Learn Redux

FAQs on the exercise Reducer Composition

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2

Originally, I use “const” to declare initialFavoriteRecipes, but I saw the answer has used “var”.
Is there any diffrence?

3
  1. “const” is immuatable,
  2. “let” and “var” are “mutable”.
  3. you can change the value of const, but you cannot change its type, admittedly this is strange to me, as something that’s “constant” usually refers to more than just the “type” that it was assigned.
  4. you can change let and var variables to whatever type you want at any point in time (but why would you)
  5. “let” is ES6 (requires transpiler - like webpack/babelfish - to run in most browsers)
  6. “var” is ES5
4

Is it common for all reducers to be defined in a singular location? For example, if you had 200 slices, would there be 200 reducers in a singular file? or can we organise these a lot better?

5

I don’t really understand why so much of the coding for the exercises so far has been done for us. Surely it would be a better learning experience to actually build the app ourselves, rather than fill in some functions in an app that CC has already created for us?

I know that I can go and practice this on my own, which is what I usually do anyway, but its annoying that I’m almost forced to do this in order to cement what I’m learning, when the perfect opportunity for this already exists within the lessons themselves.

6

How can we get the value of state.allRecipes, state.searchTerm, state.favoriteRecipes
if the default value is equal to an empty object {}?
The compiler will write “Cannot read properties of undefined”.

const rootReducer = (state = {}, action) => {
  const nextState = {
    allRecipes: allRecipesReducer(state.allRecipes, action),
    searchTerm: searchTermReducer(state.searchTerm, action),   
    favoriteRecipes: favoriteRecipesReducer(state.favoriteRecipes,action) 
  } 
  return nextState;
}

export const store = createStore(rootReducer);

We have not created any object that would store data for all slices. What will we pass as a parameter to rootReducer?

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