Why use map?

Hiya Chris! Map function is really flexible and the best thing about it is , it doesnt mutate the original array.Plus the result will be an array as well. You can loop over an array as well in a single statement without using loops. This can come really handy in React. These are the benefits of using Map function.

Now regarding your code , using ! (bang) flips the result, right? In the code , you're setting the current state. And passing in an object containing guests array. Now for current guest , you are flipping the confirmation state with !.

~ Ari

I don't see a need to use map either. You have the index already. The index provided by the app won't be out of range, since its limited to the UI on the screen. So, code provided looks unnecessarily complex. Why not just do: Kudos to Kye Buffery for the idea. See: https://teamtreehouse.com/community/can-i-change-directly-the-specific-guest

Also direct mutations to state are not a good idea. The whole idea of the way React is designed is to make thinking about state easy by making it one way and simple.

Like Kye said, see: https://reactjs.org/tutorial/tutorial.html#why-immutability-is-important

  toggleConfirmationAt = indexToChange => {
    const guestsArr = this.state.guests.slice();  // don't mutate, get copy
    guestsArr[indexToChange].isConfirmed = !guestsArr[indexToChange].isConfirmed;
    this.setState({guests: guestsArr});
  };