javascript function as class new private

1class Something {
2  #property;
3
4  constructor(){
5    this.#property = "test";
6  }
7
8  #privateMethod() {
9    return 'hello world';
10  }
11
12  getPrivateMessage() {
13      return this.#privateMethod();
14  }
15}
16
17const instance = new Something();
18console.log(instance.property); //=> undefined
19console.log(instance.privateMethod); //=> undefined
20console.log(instance.getPrivateMessage()); //=> hello worl

1// Javascript Function that behaves as class, with private variables
2function Person(name){
3    const birth = new Date();
4    this.greet = () => `Hello my name is ${name}. I was born at ${birth.toISOString()}`;
5}
6
7const joe = new Person("Joe");
8joe.greet(); // Hello my name is Joe. I was born at 2021-04-09T21:12:33.098Z
9// The birth variable is "inaccessible" from outside so "private"

1class ClassWithPrivateField {
2  #privateField;
3  
4  constructor() {
5    this.#privateField = 42;
6    this.#randomField = 666; # Syntax error
7  }
8}
9
10const instance = new ClassWithPrivateField();
11instance.#privateField === 42; // Syntax error
12