class BankAccount {
  #balance;
  #transactionLog = [];

  constructor(initialBalance) {
    this.#balance = initialBalance;
  }

  deposit(amount) {
    this.#balance += amount;
    this.#transactionLog.push(`+${amount}`);
    return this;
  }

  withdraw(amount) {
    if (amount > this.#balance) throw new Error("Insufficient funds");
    this.#balance -= amount;
    this.#transactionLog.push(`-${amount}`);
    return this;
  }

  get summary() {
    return `Balance: ${this.#balance} | Txns: ${this.#transactionLog.join(", ")}`;
  }
}

const account = new BankAccount(100);
account.deposit(50).deposit(25).withdraw(30);
console.log(account.summary);
console.log(account.hasOwnProperty("#balance"));