I have an array of objects that is basically like this.

const characters = [
{
id: 1
name: batman
biography: {
born-in: gotham
good-or-bad: good
}
stats: {
strength: 85
speed: 90
intelligence: 95
}
}
{
id: 2
name: superman
biography: {
born-in: krypton
good-or-bad: good
}
stats: {
strength: 90
speed: 85
intelligence: 80
}
}
{
id: 3
name: joker
biography: {
born-in: gotham
good-or-bad: bad
}
stats: {
strength: 70
speed: 95
intelligence: 100
}
}
]

Then, after mapping and displaying the objects in my page, I add a button that allows the user to mark the character as a favorite. The user can only add up to 6 favorites.

const [favorites, setFavorites = useState([]);

const addFavorite = () => {
favorites.length === 6 ?
console.log("favorites' list is full!") :
setFavorites(favorites.concat(character))
}

{characters.map((character)=>{
const {props} = character;
return (
<div>{props}</div>
<button onClick={addFavorite}>add to favorites</button>
);
})}

Now, what I want to do (and I don't know how to, after many attempts)

1. preventing the user to add the same character twice to favorites. (I have tried with favorites.contains(character)? or favorites.contains({character})? but it didn't work.)
2. if the character is already a favorite, make the button change to a button that removes the favorite instead (changing both the function and the button text.)(I have no idea how to do this).
3. Make an average score of all favorites' each stat. (For example, with your chosen favorites your average speed is xxx and your average strength is xxx).
4. Last, but not least, favorites list must have up to 3 good characters and 3 bad characters. So, if the good or bad characters in the favorites' list are already 3, user cannot choose another good or bad character as favorite. I also don't know how to proceed with this one.

I'm working in a school project and I found my way through most of it, but I realise I still have things to learn, mostly about object props and how to access to them. Thank you. If anything is not clear, please say so and I will add the required data.