Add toJS to return TreeNode of Tree (#639)

Co-authored-by: Youngteac Hong <susukang98@gmail.com>

src/document/crdt/tree.ts

@@ -453,9 +453,9 @@ export class CRDTTreeNode extends IndexTreeNode<CRDTTreeNode> {
 }
 
 /**
- * toJSON converts the given CRDTNode to JSON.
+ * toTreeNode converts the given CRDTTreeNode to TreeNode.
  */
-function toJSON(node: CRDTTreeNode): TreeNode {
+function toTreeNode(node: CRDTTreeNode): TreeNode {
   if (node.isText) {
     const currentNode = node;
     return {
@@ -466,7 +466,7 @@ function toJSON(node: CRDTTreeNode): TreeNode {
 
   return {
     type: node.type,
-    children: node.children.map(toJSON),
+    children: node.children.map(toTreeNode),
     attributes: node.attrs
       ? parseObjectValues(node.attrs?.toObject())
       : undefined,
@@ -679,7 +679,7 @@ export class CRDTTree extends CRDTGCElement {
       toPath: this.toPath(toParent, toLeft),
       actor: editedAt.getActorID()!,
       value: contents?.length
-        ? contents.map((content) => toJSON(content))
+        ? contents.map((content) => toTreeNode(content))
         : undefined,
     });
 
@@ -951,7 +951,14 @@ export class CRDTTree extends CRDTGCElement {
    * `toJSON` returns the JSON encoding of this tree.
    */
   public toJSON(): string {
-    return JSON.stringify(toJSON(this.indexTree.getRoot()));
+    return JSON.stringify(this.getRootTreeNode());
+  }
+
+  /**
+   * `getRootTreeNode` returns the converted value of this tree to TreeNode.
+   */
+  public getRootTreeNode(): TreeNode {
+    return toTreeNode(this.indexTree.getRoot());
   }
 
   /**

src/document/json/tree.ts

@@ -471,6 +471,17 @@ export class Tree {
     return this.tree.toJSON();
   }
 
+  /**
+   * `getRootTreeNode` returns TreeNode of this tree.
+   */
+  public getRootTreeNode() {
+    if (!this.context || !this.tree) {
+      throw new Error('it is not initialized yet');
+    }
+
+    return this.tree.getRootTreeNode();
+  }
+
   /**
    * `indexToPath` returns the path of the given index.
    */