>>Cat.prototype = new Mammal() This is only useful if Mamaml has only methods and no properties which does not happen that often. >> Cat.prototype.constructor

>>Cat.prototype = new Mammal() This is only useful if Mamaml has only methods and no properties which does not happen that often. >> Cat.prototype.constructor = Cat I never saw a practical usage of this one :-) I think these days the standard way of doing inheritance should be -> MyClass.prototype = Object.create(baseClass.prototype)