var acc = document.getElementsByClassName("accordion"); for (var i = 0; i < acc.length; i++) { acc[i].addEventListener("click", function () { var pannel = this.nextElementSibling; if (pannel && pannel.classList.contains("pannel")) { this.classList.toggle("active"); pannel.style.display = pannel.style.display === "block" ? "none" : "block"; } }); }