Simplest class toggle JS but where is the error?

Here are the codes for html, js and css. I know the internet is full of menus like this, I made this by myself and would like to know what mistake I have made. I was trying to toggle between display:none and display:box Thanks for any help.

let menu = document.getElementById("submenu");
let navbar = document.getElementById("navbar");
let showmenu = document.querySelector(".show");

function myFunction() {
    menu.classList.toggle("showmenu");
}

* {
    padding: 0;
    margin: 0;
}

nav {
    background-color: black;
    height: 38px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    
}

#submenu {
    margin-left: 5px;
}

li {
    list-style: none;
    display: block;
    float: left;
}

a {
    background-color: black;
    text-decoration: none;
    color: white;
    transition: 300ms ease-in-out;
    padding: 10px;
    text-transform: uppercase;
}

a:hover {
    background-color: rgb(0, 30, 255);
}

form {
    color: black;
    display: block;
}

button {
    background-color: rgb(0, 30, 255);
    border-radius: 10px;
    color: white;
    transition: 300ms ease-in-out;
    border: none;
    padding: 4px;
}

button:hover {
    background-color: white;
    color: rgb(0, 30, 255);
}

#burger {
    color: white;
    transition: 300ms ease-in-out;
}


#burger:hover {
    color: rgb(0, 30, 255);
    cursor: pointer;
}


@media (max-width: 700px) {
    .invisible {
        display: none;
    }

    #searchform {
        display: none;
    }

   #burger {
    display: block;
    position: absolute;
    right: 5px;
   }
   
}

.show {
    display: block;
    width: 100%;
}

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet" href="style.css">
    <script src="https://kit.fontawesome.com/6ef6e9ecfa.js" crossorigin="anonymous"></script>
    <title>Document</title>
</head>
<body>
    <header>
        <nav id="navbar">
            <ul id="submenu" class="invisible">
                <li><a href="#">Home</a></li>
                <li><a href="#">About</a></li>
                <li><a href="#">Contact</a></li>
            </ul>
            <form id="searchform">
                <input type="search" name="" id="search">
                <button onclick="myFunction()"><i class="fa-solid fa-magnifying-glass"></i></button>
            </form>
            <div id="burger"><i class="fa-solid fa-bars"></i></div>
        </nav>
    </header>
    <main></main>
    <script src="script.js"></script>
</body>
</html>

I tried to switch from querySelector to getElementBy...

Solution

you should to access burger button and add onclick to it.

let menu = document.getElementById("submenu");
let burger = document.getElementById("burger");
let form = document.querySelector("#searchform");

function myFunction() {
    menu.classList.toggle("show");
    form.classList.toggle("show");
}

* {
    padding: 0;
    margin: 0;
}

nav {
    background-color: black;
    height: 38px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    
}

#submenu {
    margin-left: 5px;
}

li {
    list-style: none;
    display: block;
    float: left;
}

a {
    background-color: black;
    text-decoration: none;
    color: white;
    transition: 300ms ease-in-out;
    padding: 10px;
    text-transform: uppercase;
}

a:hover {
    background-color: rgb(0, 30, 255);
}

form {
    color: black;
    display: block;
}

button {
    background-color: rgb(0, 30, 255);
    border-radius: 10px;
    color: white;
    transition: 300ms ease-in-out;
    border: none;
    padding: 4px;
}

button:hover {
    background-color: white;
    color: rgb(0, 30, 255);
}

#burger {
    color: white;
    transition: 300ms ease-in-out;
}


#burger:hover {
    color: rgb(0, 30, 255);
    cursor: pointer;
}


@media (max-width: 700px) {
    .invisible {
        display: none;
    }

    #searchform {
        display: none;
    }

   #burger {
    display: block;
    position: absolute;
    right: 5px;
   }
   
}

.show {
    display: block !important;
}

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet" href="style.css">
    <script src="https://kit.fontawesome.com/6ef6e9ecfa.js" crossorigin="anonymous"></script>
    <title>Document</title>
</head>
<body>
    <header>
        <nav id="navbar">
            <ul id="submenu" class="invisible">
                <li><a href="#">Home</a></li>
                <li><a href="#">About</a></li>
                <li><a href="#">Contact</a></li>
            </ul>
            <form id="searchform">
                <input type="search" name="" id="search">
                <button><i class="fa-solid fa-magnifying-glass"></i></button>
            </form>
            <div id="burger" onclick="myFunction()"><i class="fa-solid fa-bars"></i></div>
        </nav>
    </header>
    <main></main>
    <script src="script.js"></script>
</body>
</html>