Question 190039 in Javascript Question posted in
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Javascript – Random password generator keeps returning undefined

I’m trying to create a password generator for a class assignment. Every time I go through the prompt windows and select my password info I get "undefinedundefinedundefinedundefinedundefinedundefinedundefinedundefined."
I’ve been staring at this for 3 hours trying to figure it out and I’m convinced the longer I stare at it the less I know about JS. Every time I change something I make it worse. What am I doing wrong?

// Assignment Code
passwordLength = 8;
var generateBtn = document.querySelector("#generate");
var finalPassword = [];
var lowerCase = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'];
var upperCase = ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'z', ];
var characters = ['!', '@', '#', '$', '%', '^', '&', '*', '(', ')', '-', '_', '+', '=', ',', '.', '?', '<', '>', '?'];
var numbers = ['1', '2', '3', '4', '5', '6', '7', '8', '9'];
// Write password to the #password input
generateBtn.addEventListener("click", writePassword);

function writePassword() {
  var password = generatePassword();
  var passwordText = document.querySelector("#password");

  passwordText.value = password;
}

function generatePassword() {
  var randomPassword = "";
  for (let i = 0; i < passwordLength; i++) {
    let randomizer = Math.floor(Math.random() * Math.floor(passwordLength.length));
    randomPassword = +finalPassword[randomizer];
  }
  return randomPassword;
}

function promptWindow() {
  finalPassword = [];
  passwordLength = parseInt(prompt("Select a password length between 8 - 128 characters"));

  if (isNaN(passwordLength) || passwordLength <= 8 || passwordLength >= 128) {
    alert("WARNING! Invalid password length entered");
    return false;
  }
  if (confirm("Include uppercase letters in password?")) {
    finalPassword = finalPassword.concat(upperCase);
  }
  if (confirm("Include special characters in password?")) {
    finalPassword = finalPassword.concat(characters);
  }
  if (confirm("Include numbers in password?")) {
    finalPassword = finalPassword.concat(numbers);
  }
  return true;
}
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2

Answers


  1. 0

    I suspect that your problem is here on this line in generatePassword:

    let randomizer = Math.floor(Math.random() * Math.floor(passwordLength.length));

    I think you’re mistakenly using the variable passwordLength, which is a Number, so it doesn’t have a .length property. So when you run Math.floor(passwordLength.length), you’re really running Math.floor(undefined). If you run that in a console, you will get NaN back. Usually any math operation with NaN results in NaN again. So the result of all your math on that line is this:

    let randomizer = NaN;
randomPassword += finalPassword[randomizer];

    On the next line, you’re asking for the element in the Array finalPassword at the NaNth position, which doesn’t exist, so it’s undefined.

    Change that line in the generatePassword function to:

    let randomizer = Math.floor(Math.random() * finalPassword.length);

    (finalPassword.length is always an integer, so you don’t need to call Math.floor() on it.)

    That might help clear up at least some of the issues. Hope that works!

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  2. 0

    This will return undefined (passwordLength is a number)

    Math.floor(passwordLength.length)

    also need to change =+ to += on the line

    randomPassword = +finalPassword[randomizer];

    here is a peice of code generating a random password based on your initial code.

    // Assignment Code
// let passwordLength = 8;
var lowerCase = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'];
var upperCase = ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'z',];
var characters = ['!', '@', '#', '$', '%', '^', '&', '*', '(', ')', '-', '_', '+', '=', ',', '.', '?', '<', '>', '?'];
var numbers = ['1', '2', '3', '4', '5', '6', '7', '8', '9'];
var generateBtn = document.querySelector("#generate");
// var finalPassword = [];

// Write password to the #password input
generateBtn.addEventListener("click", writePassword);
function writePassword() {
    var password = promptWindow();
    var passwordText = document.querySelector("#password");
    passwordText.value = password;
}


function generatePassword(types, len) {
    var randomPassword = "";
    
    for (let i = 0; i < len; i++) {

        //pick type
        let random_type = types[Math.floor(Math.random() * types.length)] ;
        //pick character
        let random_char = random_type[Math.floor(Math.random() * random_type.length)]

        randomPassword += random_char;
    }
    return randomPassword;
}

function promptWindow() {
    finalPassword = [];
    passwordLength = parseInt(prompt("Select a password length between 8 - 128 characters"));
    let types =  [lowerCase]
    

    if (isNaN(passwordLength) || passwordLength <= 8 || passwordLength >= 128) {
        alert("WARNING! Invalid password length entered");
        return "";
    }
    if (confirm("Include uppercase letters in password?")) {
        // finalPassword = finalPassword.concat(upperCase);
        types.push(upperCase)
    }
    if (confirm("Include special characters in password?")) {
        // finalPassword = finalPassword.concat(characters);
        types.push(characters)
    }
    if (confirm("Include numbers in password?")) {
        // finalPassword = finalPassword.concat(numbers);
        types.push(numbers)
    }

    return generatePassword(types,passwordLength);
}
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