text: 
  function BankAccount() {
    this.balance = 0
  }
  
  BankAccount.prototype.deposit = function (amount, date) {
    return { date: date, amount: amount, balance: this.balance += amount }
  }
  BankAccount.prototype.withdrawal = function (amount, date) {
    if(this.balance < amount)
      throw new Error('Sorry, you balance is too low');
    return { date: date, amount: -amount, balance: this.balance -= amount }
  }
  