1var btColl = document.getElementsByClassName("collapsible");
2for (var btIter = 0; btIter < btColl.length; i++) {
3    btColl[btIter].addEventListener("click", function() {
4        document.getElementsByClassName('bt-content')[0].style.display = 'block';
5        document.getElementsByClassName('bt-warning')[0].style.display = 'none';
6    });
7}