let sidebar = document.querySelector(".sidebar"); let closeBtn = document.querySelector("#btn"); closeBtn.addEventListener("click", ()=>{ sidebar.classList.toggle("open"); menuBtnChange();//calling the function(optional) }); // following are the code to change sidebar button(optional) function menuBtnChange() { if(sidebar.classList.contains("open")){ closeBtn.classList.replace("bx-menu", "bx-menu-alt-right");//replacing the iocns class }else { closeBtn.classList.replace("bx-menu-alt-right","bx-menu");//replacing the iocns class } }