Ag-Grid Tree like structure attach cellClass to NodeChildren cells based on validation

In my Angular and angularjs application i have included Ag-Grid with columnDefs like below :-

 this.columnDefs = [   {     headerName: "Age",     field: "age",     cellRenderer: "agGroupCellRenderer"   },   {     headerName: "Name",     field: "name"   },   {     headerName: "Year",     field: "year"   },   {     headerName: "Country",     field: "country"   } ]; 

and my row Data is like below

 this.rowData = [   {     age: "Group A",     participants: [       {         age: "A.1",         name: "Michael Phelps",         year: "2008",         country: "United States"       },       {         name: "A.2",         age: "Michael Phelps",         year: "2008",         country: "United States"       },       {         name: "A.3",         age: "Michael Phelps",         year: "2008",         country: "United States"       }     ]}]; 

Now i want to attach cellClass to children grid values based on validation, like:-

 if(age< 23 || ''){   return['classNameThatiWantToAttach'];  } 

How to do this ??

You can make changes in below plunker also for this: –