Method set_root

src/jsmind.mind.js:50–59

* Set the root node, only once. * @param {string} node_id * @param {string} topic * @param {Record =} data * @returns {Node | null}

(node_id, topic, data)

     * @returns {Node | null}
     */
    set_root(node_id, topic, data) {
        if (this.root == null) {
            this.root = new Node(node_id, 0, topic, data, true);
            this._put_node(this.root);
            return this.root;
        } else {
            logger.error('root node is already exist');
            return null;
        }
    }
    /**
     * Add a child node under parent.
     * @param {Node} parent_node