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Please enable JavaScript in your browser settings or update your browser.Challenge: Implementing Private Properties in a Class | Classes
Advanced JavaScript Mastery
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Contenido del Curso

Advanced JavaScript Mastery

Advanced JavaScript Mastery

1. Classes
Welcome to the CourseClass DeclarationChallenge: Building a Class Class MethodsChallenge: Adding Methods to a ClassParameter ObjectPrivate PropertiesChallenge: Implementing Private Properties in a ClassGetters and SettersChallenge: Managing Properties with Getters and SettersStatic PropertiesStatic MethodsChallenge: Using Static Properties and Methods in a ClassInheritance with extends and Using super()Challenge: Class Inheritance with Extends and Using Super
2. DOM Manipulation
What is the DOM?Querying the DOMChallenge: Querying the DOMUnderstanding the DOM HierarchyChallenge: DOM HierarchyDOM PropertiesWorking with Element AttributesChallenge: Working with Element Properties and AttributesAdding ElementsRemoving ElementsChallenge: Adding and Removing ElementsModifying Element StylesChallenge: Modifying Element Styles
3. Events and Event Handling
Introduction to Events and Event ListenersThe Event ObjectChallenge: Events and Event ListenersEvent Propagation and DelegationChallenge: Event Propagation and DelegationKeyboard and Mouse EventsManaging Event Listeners
4. Asynchronous JavaScript and APIs
Introduction to Asynchronous JavaScriptCallbacksPromisesAsync/AwaitWorking with APIsPractical API IntegrationChallenge: Working with APIWorking with Third-Party LibrariesChallenge: Working with Third-Party LibrariesHandling Multiple Asynchronous Requests

bookChallenge: Implementing Private Properties in a Class

Task

You're creating a BankAccount class to manage users' bank accounts securely. Each account has an owner and a balance, but you want the balance to be protected from direct access. Your goal is to use private properties to prevent unintended modifications to the balance while allowing controlled access through methods.

  1. Private Balance Property:
    • Inside the BankAccount class, declare a private property #balance.
  2. Constructor:
    • The constructor should accept owner and initialBalance as parameters;
    • Assign owner to a public property and initialBalance to the private #balance property.
  3. Add Methods:
    • deposit: Define a method that takes amount as a parameter. If the amount is greater than 0, it should add amount to #balance;
    • withdraw: Define a method that takes amount as a parameter. If the amount is greater than 0 and less than or equal to #balance, it should subtract amount from #balance;
    • getBalance: Define a method that returns a string with the owner's name and the account balance, e.g., "Account balance for John: $1500".

              
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class BankAccount {
  #_____; // Declare private property

  constructor(owner, initialBalance) {
    this._____ = owner;
    this.#_____ = initialBalance;
  }

  deposit(_____) {
    if (_____) {
      this.#_____ += _____;
    }
  }

  withdraw(_____) {
    if (_____ && _____) {
      this.#_____ -= _____;
    }
  }

  getBalance() {
    return `Account balance for ${this._____}: $${this.#_____}`;
  }
}

// Testing
const account1 = new BankAccount('Alice', 1000);

account1.deposit(500);
console.log(account1.getBalance()); // Expected: Account balance for Alice: $1500

account1.withdraw(300);
console.log(account1.getBalance()); // Expected: Account balance for Alice: $1200

// Attempt direct access (should cause an error)
// console.log(account1.#balance);
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  • Declare a private property #balance in the BankAccount class;
  • In the constructor, assign owner to a public property and initialBalance to the private #balance property;
  • Define a deposit method that takes amount as a parameter. Check if amount is greater than 0, then add amount to #balance;
  • Define a withdraw method that takes amount as a parameter. Check if amount is greater than 0 and less than or equal to #balance, then subtract amount from #balance;
  • Define a getBalance method that returns a string with the owner's name and the account balance.

              
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class BankAccount {
  #balance; // Declare private property

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

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

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

  getBalance() {
    return `Account balance for ${this.owner}: $${this.#balance}`;
  }
}

// Testing
const account1 = new BankAccount('Alice', 1000);

account1.deposit(500);
console.log(account1.getBalance()); // Output: Account balance for Alice: $1500

account1.withdraw(300);
console.log(account1.getBalance()); // Output: Account balance for Alice: $1200

// Attempt direct access (should cause an error)
// console.log(account1.#balance);
copy

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Sección 1. Capítulo 8
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