function create_table_cell(content, styleClass = "") {
    if (content.trim() === "") {
        content = "<i>(üres)</i>";
    }
    let td = document.createElement("td");
    td.innerHTML = content;
    if (styleClass !== "") {
        td.classList.add(styleClass);
    }
    return td;
}

function highlight_row(nickname) {
    let hl_on = document.getElementById("user_chk_" + nickname).checked;
    let row = document.getElementById("row_" + nickname);
    row.setAttribute("highlight", hl_on ? "true" : "false");
}