Unable to read/ retrieve Sub-grid of Order entity in CRM 2015

Hi,

I am working on CRM 2015 on-premise. Wanted to retrieve first record of subgrid of Order Product which is on Order entity.

I tried to read data using JavaScript but Subgrid methods which I used were showing Object doesn’t support property or method . Strange thing is I used methods which are mentioned in SDK 2015.(methods like- getGrid(), getRows()).

Need urgent pointers on it.

Thanks in advance.

- Mugdha