How do I trigger onclick event with only one click?

It's me again! I've been slaving to get an accordion menu to work properly and I managed to get it to work... the main problem is, it only triggers on the double click of a button.

I want to make this so the user only needs to click on the button once. I have other usages of buttons in my code that work with only one click and this one does follow their formats, but I don't know whats making it trigger only on double click.

Here is the Javascript -- I could only make it work if i put it in a function(), just leaving out the function would not allow the script to work.

function accordion() {

const acc = document.getElementsByClassName("levelTab");
var a;

for (a = 0; a < acc.length; a++) {
    acc[a].addEventListener('click', function() {
        this.classList.toggle('active');
        var levelContain = this.nextElementSibling;
        if (levelContain.style.maxHeight) {
            levelContain.style.maxHeight = null;
        } else {
            levelContain.style.maxHeight = levelContain.scrollHeight + "px";
        }
    });
};
}

And the HTML

<button onclick="accordion()" class="levelTab">Cantrips</button>
                <div class="levelContain">
                    <p>
                        insert Spells here.
                    </p>
                </div>

The issue here seems to be with the way you're attaching the onclick event to your button.

You're invoking the accordion() function on a button click, and then within that function, you're attaching an additional click event listener to the levelTab class. This means that the first time you click the button, the event listener is added. On the second click, the event listener's action is executed.

You can use windows.onload to only add the event listeners when the page loads the first time.

Example on how you can fix:

Javascript

window.onload = function() {
    const acc = document.getElementsByClassName("levelTab");
    Array.from(acc).forEach((element) => {
        element.onclick = function() {
            this.classList.toggle('active');
            var levelContain = this.nextElementSibling;

            if (levelContain.style.maxHeight) {
                levelContain.style.maxHeight = null;
            } else {
                levelContain.style.maxHeight = levelContain.scrollHeight + "px";
            }
        }
    });
}

HTML

<button class="levelTab">Cantrips</button>
<div class="levelContain">
    <p>
        Insert Spells here.
    </p>
</div>