Function addHeader

docs/app/js/sanddance-app.js:10795–10799

(element, header)

    if (!condition && existing) existing.remove();
}
function addHeader(element, header) {
    const h = document.createElement("h4");
    h.innerHTML = header;
    element.insertAdjacentElement("beforebegin", h);
}
function existingHeader(element, header) {
    const { previousElementSibling  } = element;
    if (previousElementSibling && previousElementSibling.innerHTML === header) return previousElementSibling;