script.js

const characterAmountRange = document.getElementById
('characterAmountRange')
const characterAmountNumber = document.getElementById
('characterAmountNumber')

const includeUppercaseElement = document.getElementById('includeUppercase')
const includeNumbersElement = document.getElementById('includeNumbers')
const includeSymbolsElement = document.getElementById('includeSymbols')
const form = document.getElementById('passwordGeneratorForm')
const passwordDisplay = document.getElementById('passwordDisplay')

const UPPERCASE_CHAR_CODES = arrayFromLowToHigh(65, 90)
const LOWERCASE_CHAR_CODES = arrayFromLowToHigh(97, 122)
const NUMBER_CHAR_CODES = arrayFromLowToHigh(48, 57)
const SYMBOL_CHAR_CODES = arrayFromLowToHigh(33, 47).concat(
    arrayFromLowToHigh(58, 64)
    ).concat(
        arrayFromLowToHigh(91, 96)
    ).concat(
        arrayFromLowToHigh(123, 126)
    )

characterAmountNumber.addEventListener('input', synchCharacterAmount)
characterAmountRange.addEventListener('input', synchCharacterAmount)

form.addEventListener('submit', e => {
    e.preventDefault()
    const characterAmount = characterAmountNumber.value
    const includeUppercase = includeUppercaseElement.checked
    const includeNumbers = includeNumbersElement.checked
    const includeSymbols = includeSymbolsElement.checked
    const password = generatePassword(characterAmount, includeUppercase, includeNumbers, includeSymbols)
    passwordDisplay.innerText = password
})

function generatePassword(characterAmount, includeUppercase, includeNumbers, includeSymbols) {
    let charCodes = LOWERCASE_CHAR_CODES
    if (includeUppercase) charCodes = charCodes.concat(UPPERCASE_CHAR_CODES)
    if (includeNumbers) charCodes = charCodes.concat(NUMBER_CHAR_CODES)
    if (includeSymbols) charCodes = charCodes.concat(SYMBOL_CHAR_CODES)
    
    const passwordCharacters = []
    for (let i = 0; i < characterAmount; i++) {
        const characterCode = charCodes[Math.floor(Math.random() * charCodes.length)]
        passwordCharacters.push(String.fromCharCode(characterCode))
    }
    return passwordCharacters.join('')
}

function arrayFromLowToHigh(low, high) {
    const array = []
    for (let i = low; i <= high; i++){
        array.push(i)
    }
    return array
}

function synchCharacterAmount(e) {
    const value = e.target.value
    characterAmountNumber.value = value
    characterAmountRange.value = value
}