3.8 adds private fields, which are a way of declaring a class field to be unavailable outside of the containing class, including to subclasses. For example, the Person class below does not allow for anyone using an instance of the class to read the firstName, lastName or prefix

class Person {
  #firstName: string;
  #lastName: string;
  #prefix: string;

  constructor(firstName: string, lastName: string, prefix: string) {
    this.#firstName = firstName;
    this.#lastName = lastName;
    this.#prefix = prefix;
  }

  greet() {
    // In iceland it is preferable to use a full name instead of [prefix] [lastname]
    // https://www.w3.org/International/questions/qa-personal-names#patronymic
    if (navigator.languages[0] === "is") {
      console.log(`Góðan dag, ${this.#firstName} ${this.#lastName}`);
    } else {
      console.log(`Hello, ${this.#prefix} ${this.#lastName}`);
    }
  }
}

let jeremy = new Person("Jeremy", "Bearimy", "Mr");

// You can't get to any of the private fields from outside that class:

// For example, this won't work:
console.log(jeremy.#lastName);

// Nor this:
console.log("Person's last name:", jeremy["#lastName"]);

class Dog {
  private _name: string;
  constructor(name: string) {
    this._name = name;
  }
}

let oby = new Dog("Oby");
// Won't let you access via dot notation
oby._name = "Spot";
// But TypeScript allows bracket notation as an escape clause
oby["_name"] = "Cherny";