This is a test script to test the new "private fields" in classes. (May not work now due to incomplete implementation)

test_privateFields_es2020.js

class PrivateNameTest{
  #lucky_number; //This hopefully can be tried without the semicolon once the proposal is implemented.
  constructor(){
    this.#lucky_number = 42;
  }
  guessLuckyNumber(guessedNumber){return guessedNumber===this.#lucky_number;}
}

class PrivateDefTest{
  #arePrivateVariablesAwesome = true;
  constructor(){}
  amIAwesome(){return this.#arePrivateVariablesAwesome;}
}

class PrivateMethodTest{
  
  #RNG(max,min){
  //if methods doesn't work but variables do, put "=function" in between the "RNG" and "()"
    return Math.ceil( ( Math.random() * (max - min + 1) ) + (min - 1) );
  }
  
  #diceSides;
  constructor(sideCount){
    this.#diceSides = sideCount;
  }
  roll(){
    return this.#RNG(this.#diceSides,1);
  }
}

//If those won't give syntax errors, code below will run.
console.log((new PrivateNameTest()).guessLuckyNumber(3)); //false

console.log((new PrivateDefTest()).amIAwesome()); //true

console.log((new PrivateMethodTest(6)).roll()); //some number between 1-6

The proposal if you want to know more.