Support Control Props for all state

Hi Kent. Is there any reason you've used an if/else and mutated the object here over using object spread, a ternary and computed properties? Seems cleaner to use the latter:

getState() {
    return Object.entries(this.state).reduce(
      (combinedState, [key, value]) => ({
        ...combinedState,
        [key]: this.isControlled(key) ? this.props[key] : value
      }),
      {}
    )
  }

I believe they're functionally equivalent, and appreciate the former is easier to digest if you're not used to these language features, but this an advanced course and you've not shied away from these features in previous episodes so I was curious.

I honestly hadn't considered that 💯