Edit code inside a localscript?

How do I edit the code inside a local script and run it? Games like Void Script Builder has done it and it's still functional.

You cannot edit a LocalScript's source at runtime.

Void SB doesn't do that either. What they do is upload a new model to roblox containing the localscript and then insert it in game using either require() or InsertService:LoadAssetVersion(), not sure.