Can you give an example of encapsulation in object-oriented programming?

Encapsulation is an OOP principle that allows hiding the internal implementation details of an object and providing access to data and methods through a public interface.

Example in JavaScript (Node.js):

class BankAccount {
  #balance; // private field

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

  deposit(amount) {
    if (amount > 0) {
      this.#balance += amount;
    }
  }

  withdraw(amount) {
    if (amount > 0 && amount <= this.#balance) {
      this.#balance -= amount;
      return amount;
    }
    return 0;
  }

  getBalance() {
    return this.#balance;
  }
}

const account = new BankAccount(1000);
account.deposit(500);
console.log(account.getBalance()); // 1500
// Cannot directly change the balance:
// account.#balance = 100000; // Error

Here, the #balance field is hidden from external access, which protects the data from incorrect modification.