meet it

Private fields lock data in; getters let people peek.

Unit 1 hid data in closures. Classes have their own lock: a name starting with # is a . Only code inside the class body can touch #balance. Outside the class, even mentioning it is a SyntaxError.

A , written get balance(), runs when someone reads account.balance, so they can look but not change. Writing to it throws a TypeError in , the careful setting Gwecode always runs your code in. A method, like Account.fromPounds, belongs to the class itself.

class Account {
  #balance = 0;
  static fromPounds(pounds) {
    const account = new Account();
    account.deposit(pounds * 100);
    return account;
  }
  deposit(pence) {
    if (pence > 0) { this.#balance = this.#balance + pence; }
  }
  get balance() { return this.#balance; }
}
const savings = Account.fromPounds(12);
console.log(savings.balance, savings);

The console shows {} for savings because private fields are never printed or copied.

guess first

A thermostat with a getter. What happens?

Guess before you run it. Wrong guesses are how you learn, and nothing is marked.

class Thermostat {
  #celsius = 20;
  get celsius() { return this.#celsius; }
  warmer() { this.#celsius = this.#celsius + 1; }
}
const hall = new Thermostat();
hall.warmer();
console.log(hall.celsius);
hall.celsius = 30;
console.log(hall.celsius);

your turn

Your turn. Write a getter for a full name.

Finish the getter so it adds the private last name, then make a customer with a first and last name of your choice.

Your code

press run to see what happens

fix it

The cart count crashes. Can you fix it?

Broken code to fix

press run to see what happens

Look at how count is defined on line 4. Is it an ordinary method?
A getter is read like a property. cart.count is already the number 2, and you cannot call a number.
On the last line, change cart.count() to cart.count, then press run.

nailed it

your classes keep their secrets. :D

A # name is a private field, sealed inside the class.
A getter is read like a property, with no brackets.
Static methods belong to the class, not each instance.

new words in your collection

private field
getter
static
strict mode

This lesson isn’t saved. A free account remembers every lesson you finish.