LESSON 628 OF 671 · OBJECT-ORIENTED PROGRAMMING

Private Fields in JavaScript

Lesson

TL ; DR:

Modern JavaScript (ES2022+) has true private fields with the # prefix:

class Dog {
    #name;

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

    getName() {
        return this.#name;
    }
}

Outside the class, rex.#name is a syntax error — the runtime enforces it.
Older code uses the underscore convention (this._name), which is just a hint and not enforced.

Full lesson:

For decades, JavaScript classes had no real privacy — programmers used a leading underscore (_name) as a convention. ES2022 added true private fields with the # prefix.

How # private fields work

You must declare the field at the top of the class body: #name;
You access it as this.#name — never as a string or via this[...].
Trying to access from outside is a syntax error, not a runtime error.

Your task

The Dog class declares #name and the constructor stores into it. Add a getName() method that returns this.#name.

Dog's name: Rex

STEP 1 OF 2

Guided

Ctrl + Enter to check