ElementUI 折叠tree全部节点

// tree为Tree组件的ref值
// node-key="id" 必须添加到 el-tree 节点上
this.$nextTick(() => {
    for(let i = 0; i < this.$refs.tree.store._getAllNodes().length; i++){
        this.$refs.tree.store._getAllNodes()[i].expanded = false;
    }
});