wiki-grav/plugins/form/templates/forms/layouts/xhr.html.twig

{% if form.xhr_submit == true %}
  {% do assets.addJs('plugin://form/assets/xhr-submitter.js', {'group': 'bottom', 'position': 'before'}) %}
  {% do assets.addInlineJs("
    document.addEventListener('DOMContentLoaded', () => {
        attachFormSubmitListener('" ~ form.id ~ "');
    });",
    {'group': 'bottom', 'position': 'before'}) %}
{% endif %}