code: function getFocusElements(elm) {
          var elements = [];
  
          function collect(elm) {
            if (elm.nodeType != 1 || elm.style.display == 'none' || elm.disabled) {
              return;
            }
  
            if (canFocus(elm)) {
              elements.push(elm);
            }
  
            for (var i = 0; i < elm.childNodes.length; i++) {
              collect(elm.childNodes[i]);
            }
          }
  
          collect(elm || root.getEl());
  
          return elements;
        }
docs: Returns an array of focusable visible elements within the specified container element.
  
  @private
  @param {Element} elm DOM element to find focusable elements within.
  @return {Array} Array of focusable elements.