index.js

const passwordBox = document.getElementById("password");
const copyBtn = document.getElementById("copy");
const generateBtn = document.getElementById("generate");
const length  = 12;
const uppercase = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
const lowercase = "abcdefghijklmnopqrstuvwxyz";
const numbers = "0123456789";
const symbols = "!@#$%^&*()_+<>?";
const allChars = uppercase + lowercase + numbers + symbols;
function createPassword(){
    let password="";
    password += uppercase[Math.floor(Math.random() * uppercase.length)];
    password += lowercase[Math.floor(Math.random() * lowercase.length)];
    password += numbers[Math.floor(Math.random() * numbers.length)];
    password += symbols[Math.floor(Math.random() * symbols.length)];
    while(password.length < length){
        password += allChars[Math.floor(Math.random()*allChars.length)];
    }
    passwordBox.value = password;
}

function copyPassword(){
    passwordBox.select();
    document.execCommand("copy");
}