Prompts the user to guess the number the computer generated

Number Guesser

//set up before the main algorithm
let prompt = require("prompt-sync")();
//in the case that the answer is not a number.
const isNumber = function() {
  while (Number(answer) === NaN){
  console.log('Not a number! Try again!');
  answer = prompt("Guess a number: ");
  }
}

//generate a random number between 1 to 1000
let solution = Math.ceil(Math.random()*1000);
//get the first answer from the user
let answer = prompt("Guess a number: ");
//to track all attempts
let solutionTracker = [];

//ensures the input is a number, before entering the while loop
isNumber();
while ((answer !== solution)){
  if (solutionTracker.includes(answer)){
    console.log('Already Guessed!');
  }else if (answer < solution){
    console.log('Too low');
  }else if (answer > solution){
    console.log('too high');
  }
  solutionTracker.push(answer);
  if (answer == solution){
    let attempts = [...new Set(solutionTracker)].length;
    if (attempts === 1){
      console.log(`You got it! You took ${attempts} attempt!`);  
    }else {
      console.log(`You got it! You took ${[...new Set(solutionTracker)].length} attempts!`);
    }
    break;
  }
  //asks for another guess for the next iteration
  answer = prompt("Guess a number: ");
  //ensures the input is a number before re-rentering the while loop
  isNumber();
}

//personal comment: I don't really like my solution that much. I feel like using in-built methods might make the algorithm less efficient. I would love some feedback.