Generator-based slot machine game

generator-slot-game.js

const getRandomInt = (range) => Math.floor(Math.random() * range);

// Create an array of symbols for the slot machine
const symbols = ['🍒', '🍋', '🔔', '7️⃣', '🎱'];

// Define a generator function that will yield a random symbol 
// from the array when iterated over
function* getReels(noOfReels = 3) {
  let i = 0;
  while (i++ < noOfReels) {
    yield symbols[getRandomInt(symbols.length)];
  }
}

function* getSlotMachine() {
  let balance = 0;
  let betSize = 10;
  let round = 1;

  while (balance === 0) {
    console.log('Please deposit coins!');
    const deposit = yield balance;
    balance += isNaN(deposit) ? 0 : deposit;
  }

  console.log('Game started!');
  console.log(`Balance: ${balance}`);

  while (balance > 0) {
    // Consume any new coins
    const deposit = yield balance;
    balance += isNaN(deposit) ? 0 : deposit;

    // Play game round, if enough balance
    if (balance - betSize < 0) {
      break;
    }
    console.log(`ROUND ${round++} BEGIN`);
    balance -= betSize;

    const result = [...getReels()];
    // If we land three symbols in a row, we win
    // A set can not contain duplicates
    // A set with size 1 means there are 3 duplicates, hence we win
    const areSame = new Set(result).size === 1;

    // Print reader-friendly result
    console.log(result.join(' | ')); // 7️⃣ | 🍒 | 🍒

    if (areSame) {
      // Find the weight of the winning symbol
      const winSize = symbols.indexOf(result[0]);
      const winInCoins = betSize * (winSize + 1);
      // Calculate win using the weight of the index of the symbol
      console.log(`You won ${winInCoins} coins!`);
      balance += winInCoins;
    } else {
      console.log('No win');
    }

    console.log(`Balance: ${balance}`);
  }

  console.log('Game over!');
  return 0;
}

let state;
const game = getSlotMachine();
game.next(); // "Please deposit coins"
state = game.next(30); // "Game started!"

// Autoplay
while (state.value > 0) {
  state = game.next();
}