Why does my Redux reducer think my state is undefined?

Question

I believe I\'m copying the Todo tutorial pretty much line for line, I am getting this error:

Error: Reducer \"addReport\" returned undefined during in

Answer 1

You are missing the default of the switch case.

default: {
  return {
    ...state
  }
}

Redux won't play along like a nice kid if you forget to do it!

Or alternatively, you can explicitly return at the end the initial state: If the state passed to the reducer is undefined, you must explicitly return the initial state.