The current ESNext contains a proposal for private members; for example:

class Person {

    #firstName;
    #lastName;

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

    toString() {
        return `${this.#firstName} ${this.#lastName}`;
    }
}

const person = new Person("John", "Smith");
const firstName = person.firstName; // ERROR: Property 'firstName' does not exist on type 'Person'.
const fullName = person.toString(); // John Smith

TypeScript has supported public, protected and private members (IIRC) since the very beginning, although they are erased since there is no JavaScript equivalent.

What I want to know is, whether TypeScript can be configured (current, on roadmap, or being discussed) to support mapping private to ESNext private members; for example:

class Person {

    constructor(private firstName: string = "", private lastName: string = "") {

    }

    toString() {
        return `${this.firstName} ${this.lastName}`;
    }
}

Compiled (Target = ESNext)

class Person {

    #firstName;
    #lastName;

    constructor(firstName = "", lastName = "") {
        this.#firstName = firstName;
        this.#lastName = lastName;
    }

    toString() {
        return `${this.#firstName} ${this.#lastName}`;
    }
}

Compiled (Target <= ES2021)

"use strict";
class Person {
    constructor(firstName = "", lastName = "") {
        this.firstName = firstName;
        this.lastName = lastName;
    }
    toString() {
        return `${this.firstName} ${this.lastName}`;
    }
}