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  • Karl Giesing thinks this is interesting:

These instances have copies both of the general Task defined behavior as well as the specific XYZ defined behavior.

From

Cover of You Don't Know JS: this & Object Prototypes

Note

Nope, they sure don't. They're not "copies of" the behavior, they're references to that behavior (as implemented by some kind of abstract data, i.e. a vtable).