how to get parent case values via xrm?

Hello - I have a requirement where I need to give users the ability to create child cases. There are about 10 case form field values that the users want copied from the parent case to the child case by default. It seems like I need to do this through Xrm via the onload function in the case js, so the form is pre-populated with the expected values, which the user can then modify.

However, I'm not sure about the best way to go about doing this. It looks like, when I select Case > Children from the left nav bar, and then click the "Add New Case" button, CRM opens a new Case form with a _CreateFromId parameter in the query string.

I could probably make an oData call from the js to retrieve the parent entity by this ID but I wasn't sure if there was a quicker, more appropriate Xrm function build into the framework that would be more appropriate to use for this?