Thank you very much for your detailed and helpful answer! I really appreciate the modern async/await approach you shared — it definitely improves readability, especially for more complex asynchronous logic. For now, I’ve decided to stick with my current Promise-based version, as it's a bit simpler for this use case and fits better with the rest of my codebase, which mostly uses .then() chains. Still, I fully agree that async/await is the cleaner and more scalable solution, and I’ll likely switch to it as the project grows. Thanks again for your guidance — it was very insightful! Here’s the version I’m currently using:

function fillTable(tablehead, tablebody, url) { 
return fetch(url)
    .then(res => res.json())
    .then(data => {
        if (!Array.isArray(data) || data.length === 0) return;

        let fejlec = '<tr>';
        for (let key in data[0]) {
            fejlec += `<th>${key}</th>`;
        }
        fejlec += '</tr>';

        let sorok = '';
        data.forEach(sor => {
            sorok += '<tr>';
            for (let key in sor) {
                sorok += `<td>${sor[key]}</td>`;
            }
            sorok += '</tr>';
        });

        $(`#${tablehead}`).html(fejlec);
        $(`#${tablebody}`).html(sorok);
    })
    .catch(error => {
        console.error('Error loading table:', error);
    });

}