1:  let total = 0;

   2:  const prices = [10, 20, 30];

   3:  

   4:  // Side effect: Modifying the 'total' variable outside the callback

   5:  prices.forEach(price => {

   6:      total += price; // Modifies external state

   7:  });

   8:  

   9:  console.log(total);