getPreviousSiblingWithClass.js

function getPrevious(n, className) {
  var y = n.previousSibling;
  // Check if previous node is an element node with a specific class
  while (y.nodeType != 1 || !y.classList.contains(className)) {
      // If not, move on to previous node
      y = y.previousSibling;
  }
  return y;
}