Hangman same letter cannot be used again javascript

Question

I am trying to run a program that makes the user guess the word by typing in the letter. The same letter should not be allowed to be inputted twice. I was thinking of storing each letter inputted in a list and then I would loop through the list checking each element against the user input. If it is inputted twice and error message like try again will occur. This is what I have so far.

var x = ["Football", "Pie", "Red", "Amber", "Purple", "Blue"];                                                  
var y = x[Math.floor(Math.random() * x.length)].toLowerCase();                                                  
var answerArray = [];                                                   
var lettersUsed = [];                                                   
var numberOfGuesses = 10;                                                   
for (var i = 0; i < y.length; i++)                                                  
{                                                   
  answerArray[i] = "_";                                                 
}                                                   
var remainingLetters = y.length;                                                    
while (remainingLetters > 0 && numberOfGuesses > 0)                                                 
{                                                   
  console.log(answerArray.join(" "));                                                   
  var guess = prompt("Guess a letter\n");                                                   
  if (guess === null)                                                   
  {                                                 
    console.log("Game over");                                                   
    break;                                                  
  }                                                 
  else if (guess.length !== 1)                                                  
  {                                                 
    console.log("Enter a single letter\n");                                                 
  }                                                 
  else                                                  
  {                                                 
    numberOfGuesses--;                                                  
    lettersUsed.push(guess);                                                    
    for (var j = 0; j < y.length; j++)                                                  
    {                                                   
      if (y[j] === guess.toLowerCase() && answerArray[j] === "_")                                                   
      {                                                 
        answerArray[j] = guess.toLowerCase();                                                   
        remainingLetters--;                                                 
      }                                                 
    }                                                   
  }                                                 
}                                                   
console.log(answerArray.join(" "));                                                 
if (numberOfGuesses > 0)                                                    
{                                                   
  console.log("Well done! You've won! Your stick guy has been saved!\n");                                                   
}                                                   
else                                                    
{                                                   
  console.log("Game over! The word was " + y);                                                  
}                                                   
///console.log(lettersUsed);

How do I write the for loop? Any help would be appreciated.

Answer 1

You can use the Array.includes(item) method. It will return true if the item is in the array. For example:

let lettersUsed = ['a', 'b', 'c'];
let newLetter = 'b';
if (lettersUsed.includes(newLetter)) {
  console.log('letter already used');
} else {
  console.log('letter not used yet');
}

Edit in response to question from OP:

You could add this after you check the input length:

  else if (guess.length !== 1)
  {
    console.log("Enter a single letter\n");
  } 
  else if (lettersUsed.includes(guess))
  {
    console.log('Letter already used');
  }
  else
  {
    numberOfGuesses--;