[Medium] reducer with ImmutableJS

reducer.js

export default (action, state) => {
  switch(action.type) {
   case FIRST_EXAMPLE:
      return state
        .updateIn(
          ["dfes", "nfes", "data", action.index],
          data => data.set("visible", true)
        )
        .setIn("quickbarIsOpen", true)
    default:
      return state
  }
}