My solution with easy changeable values option.

const main = document.querySelector('main');
let randomNumber;
let guess;
const upper = 6;
const guessChancesNumber = 3;
const gameRules = alert(`Hello !
You are about to play a guessing game. 
The machine is thinking to a number and you have ${guessChancesNumber} chances to guess it. Good luck ! `);

function getRandomNumber(upper) {
  return Math.floor(Math.random() * upper) + 1;
};
for (i = 1; i <= guessChancesNumber; i++) {
  randomNumber = getRandomNumber(upper);
  console.log(randomNumber);
  guess = prompt(`I am thimking of a number betweeen 1 and ${upper}. What is it ?`);
  if (parseInt(guess) == randomNumber) {
    main.innerHTML = `<h1> It was ${randomNumber} .You guessed it ! Congrat !!!</h1>`;
    break;
    // Terminate the loop if the user guesses the number
  } else {
    // The game is over because the user have no more guessing chances left.
    main.innerHTML = `<h1> It was number ${randomNumber} .You have ${guessChancesNumber - i} guesses left! Try again.</h1>`;
  }
};