This seems simple enough but can't determine what event should I look in to.
Sample code:
let forms = document.getElementsByTagName('form');
forms[0].addEventListener('submit', () => {
document.getElementById('submit').disabled = true;
});
<form action="submit.html" method="post">
<input type="submit" id="submit" value="Submit" />
</form>
The code above will disable the submit button upon submit. How do you enable it again when you hit the browser back button?