el-tree全部展开全部折叠方法

// 折叠所有节点
setAllFold() {
  for (var i = 0; i < this.$refs.tree.store._getAllNodes().length; i++) {
    this.$refs.tree.store._getAllNodes()[i].expanded = false;
  }
},
// 展开所有节点
setAllExpand() {
  for (var i = 0; i < this.$refs.tree.store._getAllNodes().length; i++) {
    this.$refs.tree.store._getAllNodes()[i].expanded = true;
  }
}