code: function insertBefore(parent, child, index) {
              var parentEl = parent.el,
                  childEl = child.el;
              if (parentEl !== undefined && childEl !== undefined) {
                  if (parentEl.childNodes[index] !== undefined) {
                      parentEl.insertBefore(childEl, parentEl.childNodes[index]);
                  } else {
                      parentEl.appendChild(childEl);
                  }
              }
          }
docs: Insert element to the before of specific, child by index  @method insertBefore @param {dom.Element} parent @param {dom.Element} child