script.js

const resultEl = document.getElementById(`result`);
const lengthEl = document.getElementById(`length`);
const upperCaseEl = document.getElementById(`uppercase`);
const lowerCaseEl = document.getElementById(`lowercase`);
const numbersEl = document.getElementById(`numbers`);
const symbolsEl = document.getElementById(`symbols`);
const generateEl = document.getElementById(`generate`);
const clipboardEl = document.getElementById(`clipboard`);

const randFunc = {
    lower: getRandomLower,
    upper: getRandomUpper,
    number: getRandomNumber,
    symbol: getRandomSymbol
};

clipboardEl.addEventListener('click', () => {
    const textarea = document.createElement('textarea');
    const password = resultEl.innerText;

    if (!password)
        return;

    textarea.value = password;
    document.body.appendChild(textarea);
    textarea.select();
    document.execCommand('copy');
    textarea.remove();
    alert(`Password copied to clipboard!`);
})

generateEl.addEventListener('click', () => {
    const length = +lengthEl.value;
    const hasLower = lowerCaseEl.checked;
    const hasUpper = upperCaseEl.checked;
    const hasNumber = numbersEl.checked;
    const hasSymbol = symbolsEl.checked;

    resultEl.innerText = generatePassword(hasLower, hasUpper, hasNumber, hasSymbol, length);
})

function generatePassword(lower, upper, number, symbol, length) {
    let generatedPassword = ``;
    const typesCount = lower + upper + number + symbol;

    const typesArr = [{ lower }, { upper }, { number }, { symbol }].filter(item => Object.values(item)[0])

    if (typesCount === 0)
        return '';

    for (let i = 0; i < length; i += typesCount) {
        typesArr.forEach(type => {
            const funcName = Object.keys(type)[0];
            generatedPassword += randFunc[funcName]();
        })
    }

    const finalPassword = generatedPassword.slice(0, length);

    return finalPassword;
}

function getRandomLower() {
    return String.fromCharCode(Math.floor(Math.random() * 26) + 97);
}

function getRandomUpper() {
    return String.fromCharCode(Math.floor(Math.random() * 26) + 65)
}

function getRandomNumber() {
    return String.fromCharCode(Math.floor(Math.random() * 10) + 48)
}

function getRandomSymbol() {
    const symbols = '!@#$%^&*(){}[]=<>/,.'
    return symbols[Math.floor(Math.random() * symbols.length)]
}