dist/vue-draggable-nested-tree.es.js
function targetNodeIs1stChild(info) {
    return findChild(info, info.targetNode.parent.children, function (v) {
      return v;
    }) === info.targetNode;
  }
function targetNodeIs1stChild(info) {
    return findChild(info, info.targetNode.parent.children, function (v) {
      return v;
    }) === info.targetNode;
  }
另一节点是第一个节点