//Declare variable, add class name to get elements by class name
                var semesters = document.getElementsByClassName("semester");

                for (let i = 0; i < semesters.length; i++) {
                var semester = semesters[i];
                // Toggle between adding and removing the "active" class, to highlight the button that controls the panel
                semester.addEventListener("click", function () {
                this.classList.toggle("active");

                var courses = this.nextElementSibling;
                //Slide down the content by setting a calculated max-height, depending on the panel's height on your screen size.
                if (courses.style.maxHeight) {
                    courses.style.maxHeight = null;
                } else {
                    courses.style.maxHeight = courses.scrollHeight + "px";
                }
            });
        }