Conditionally adding object methods

I stumbled my way into an interesting experiment today where I discovered that, within a JavaScript constructor function, one might conditionally add a method based on whether the prototype has that method already or not.

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This code ensures that when the method `bar` exists on the prototype for Foo, the instance implementation of `bar` added in Foo’s constructor won’t be applied. So the instance implementation is kind of like a “default implementation”.This m...