Object.defineProperty is ultra slow. Test case attached. I am adding 1 property to a fresh object 3000000 times. It takes 20 seconds with Object.defineProperty, 0.8 sec without.

90% of the time is spent in jdk.nashorn.internal.runtime.ScriptObject.deleteObject (called from jdk.nashorn.internal.objects.NativeObject.defineProperty) although my objects are fresh, no state to delete (I guess).