element-ui el-tree手动展开/折叠全部节点

方法一：

this.setAllExpand1(true); // 全部展开

setAllExpand1(state) {
    for (let i = 0; i < this.$refs.tree.store._getAllNodes().length; i++) {
        this.$refs.tree.store._getAllNodes()[i].expanded = state;
    }
},

方法二：

this.setAllExpand2(true); // 全部展开

setAllExpand2(state) {
    var nodes = this.$refs.tree.store.nodesMap;
    for (var i in nodes) {
        nodes[i].expanded = state;
    }
},