document.queryselectorLast code example
Example: document.queryselector picks first or last
var elFirst = document.querySelector(".myclass"); //first element
var elLast = document.querySelector(".myclass:last-child"); //last element
But be careful!
:last-child and :first-child are relevant to the parent element,
not to the list! It means that there could be several first-childs
and several last-childs