Remove validation and prompt when exiting unsaved form

form.html

<script>
    const forms = Array.from(document.querySelectorAll("form"))

    // disable browser validation
    forms.forEach(el => el.noValidate = true)

    // add unsaved data prompt
    let unsaved = false;
    window.addEventListener("beforeunload", (e) => {
        if (unsaved) {
            e.preventDefault();
            e.returnValue = "";
        } else {
            delete e['returnValue'];
        }
    })

    /**
     * @param {HTMLFormElement} el
     */
    function markUnsaved(el) {
        if (!el.target.dataset.ignoreUnsaved) unsaved = true;
    }

    /**
     * @param {HTMLFormElement} el
     */
    function unmarkUnsaved(el) {
        unsaved = false;
    }

    forms.forEach(el => {
        el.addEventListener('change', markUnsaved);
        el.addEventListener('submit', unmarkUnsaved);
    })
</script>