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 clipboard = document.getElementById('clipboard');

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

clipboard.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');
});

// GENERATE EVENT LISTEN
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);
});

// GENERATE PASSWORD FUNCTION
function generatePassword(lower, upper, number, symbol, length) {
    // Init Password var
    let generatedPassword = '';
    const typesCount = lower + upper + number + symbol;
    const typesArr = [{
        lower
    }, {
        upper
    }, {
        number
    }, {
        symbol
    }].filter(item => Object.values(item)[0]);

    // Doesn't have a selected type
    if (typesCount === 0) {
        return '';
    }

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

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

// FUNCTIONS GENERATOR
// lower Alphabet
function getRandomLower() {
    return String.fromCharCode(Math.floor(Math.random() * 26) + 97);
}
// Upper Alphabet
function getRandomUpper() {
    return String.fromCharCode(Math.floor(Math.random() * 26) + 65);
}
// Numbers
function getRandomNumber() {
    return String.fromCharCode(Math.floor(Math.random() * 10) + 48);
}
// Symbols
function getRandomSymbol() {
    const symbols = "!@#$%^&*(){}[]=<>/,."
    return symbols[Math.floor(Math.random() * symbols.length)];
}