Using mod operator in JavaScript to wrap around

Question

I am building a Texas Hold'em Poker web application using ReactJS. In order to keep track of the dealer button, I am using the following formula...

let currentPlayers = [
    {name: "Foo", position: 1}, 
    {name: "Bar", position: 2},
    {name: "Baz", position: 3} 
]
let dealerButtonPos = 1

dealerButtonPos = ((dealerButtonPos + currentPlayers.length ) % currentPlayers.length + 1 )

What I am trying to do here is make sure that the dealer button starts at position 1 and is always on the correct position at the start of every round. The dealer button, in this case, should always fall on position 1, then 2, then 3, then 1 again.

The function with the formula will be called at the end of every round. This should rotate the dealer button correctly for up to 8 players. Will I always be on the correct player position? Am I implementing this correctly? I had a hard time conceptualizing and getting to this point. Can someone explain the mod operator for clarity?

Answer 1

Be nice for iterator pattern

let currentPlayers = [
    {name: "Foo", position: 1}, 
    {name: "Bar", position: 2},
    {name: "Baz", position: 3} 
]

function* currentPlayersIterator(players) {
  let index = 0;
  while(true)
    if (index < players.length) {
      yield players[index++]
    } else {
      index = 0
      yield players[index++]
    }
}


let i = currentPlayersIterator(currentPlayers)

console.log(i.next().value)
console.log(i.next().value)
console.log(i.next().value)
console.log(i.next().value)
console.log(i.next().value)