elment 中tree组件展开所有和收缩所有节点

 //收起所有节点
            setCheckedKeys() {
                this.defaultExpand = false;
                for (var i = 0; i < this.$refs.tree.store._getAllNodes().length; i++) {
                     if (this.$refs.tree.store._getAllNodes()[i].id !== 1) {
                         this.$refs.tree.store._getAllNodes()[i].expanded = this.defaultExpand;
                    }
                }
            },

            setCheckedNodes() {
                this.defaultExpand = true; //展开所有节点
                for (var i = 0; i < this.$refs.tree.store._getAllNodes().length; i++) {
                    this.$refs.tree.store._getAllNodes()[i].expanded = this.defaultExpand;
                   
                }
            }