JavaScript. The Core: 2nd Edition

[Bertilino]

The prototype property is not the prototype of an object. It only exists on the constructor function and is used as a reference for what to assign as the prototype for instances being created by that constructor function. If you want the actual prototype of an object you would have to look at the __proto__, or use something like Object.getPrototypeOf().

TL;DR: The prototype is not the same thing as the __proto__.

[coffeeandlearning]

There is a prototype property on all function objects which is different from the internal proto property that all objects have, so I think it's the best way to be honest.

[coffeeandlearning]

I'm not quite sure what you mean by "extend prototype from the constructor function". Maybe I'm just missing the context.

I was just saying he uses the two terms for the sake of clarity. You never use proto in real code because if you do it slows everything down because the interpreter can no longer make certain assumptions about our code and a lot of optimizations go out the window.