Why is it important to use encapsulation in object-oriented systems?

Encapsulation is a principle of object-oriented programming that allows hiding the internal details of an object and providing access to data only through specific methods. This is important because:

• It protects data from incorrect or unintended external modification.
• It simplifies support and modification of code, as internal changes do not affect the external interface.
• It increases readability and structure of the code.
• It allows controlling access and data validation.

An example in Node.js using classes and private fields:

class User {
  #password; // private field

  constructor(name, password) {
    this.name = name;
    this.#password = password;
  }

  checkPassword(input) {
    return input === this.#password;
  }
}

const user = new User('Alice', 'secret');
console.log(user.name); // Alice
console.log(user.#password); // Error: private field
console.log(user.checkPassword('secret')); // true

Thus, encapsulation helps create more reliable and maintainable systems.