js uses a recursive method to obtain multi-level keys

JS uses a recursive method to obtain multi-level key values.
The requirements are as follows: a subset of the list is to be expanded by default. The official property is ' defaultExpandedRowKeys ', which must be an array

 componentDidMount(){
    
    
    const {
    
    dataSource} = this.state; 
    const getTableKey = (data) => {
    
    
    const parentKey = [];
    data.forEach((item) => {
    
    
      if (item.subList && item.subList.length) {
    
    
          parentKey.push(item.key);
          const temp = getTableKey(item.subList);
          if (temp.length) {
    
    
              parentKey.push(...temp);
          }
      }
    });
    return parentKey;
    }; 
    const arrKey = getTableKey(dataSource); 
    this.setState({
    
    arrKey}) 
  };

<Table 
     columns={
    
    columns}  
     dataSource={
    
    dataSource}  
     childrenColumnName="subList" 
     bordered
     pagination={
    
    false}
     defaultExpandedRowKeys={
    
    this.state.arrKey}  
   />

as the picture shows:

Note: The article focuses on this recursive method, because the structural subset of the table is unknown, so the recursive method is the best solution;