Javascript prototypal inheritance weirdness

I'm trying to work through some javascript inheritance examples and I hit a wall with this one:

function Animal(){}
Animal.prototype.type = "animal";
Animal.prototype.speak = function(){ console.log( "I'm a " + this.type + 
    ". I can't really talk ;)" ); }

function Dog(){}

function F(){}
F.prototype = Animal.prototype;

Dog.prototype = new F();
Dog.prototype.constructor = Dog;
Dog.prototype.type = "Dog";
Dog._super = Animal.prototype;
Dog.woof = function(){ console开发者_JS百科.log( "Woof!" ); _super.speak(); }

var rover = new Dog();
rover.woof();

I am getting this and I have no idea why:

TypeError: Object #<Dog> has no method 'woof'

I know I can put the not-found method into the constructor function, but I am trying to do this with prototype modification. What am I doing wrong here?

Change:

Dog._super = Animal.prototype;
Dog.woof = function(){ console.log( "Woof!" ); _super.speak(); }

To:

// Dog.prototype._super = Animal.prototype; <- you can remove this line
Dog.prototype.woof = function(){ console.log( "Woof!" ); this.speak(); }

The last string of the Dog pseudo-class definition is wrong. It should be

Dog.prototype.woof = function(){ console.log( "Woof!" ); Dog._super.speak.call(this); }

1. You should define method woof as the property of the Dog's prototype.
2. _super is available only as the property of the Dog constructor.
3. You should call the methods of the parent class in context of the current instance.

So your woof method is actually effectively a static method (If you're coming from java. Basically, it's hanging off the Dog function, and can be accessed without an instance of Dog. ie: Dog.woof())

To get it working with an instance of a dog, you want to make sure it's a prototype definition (again, with a Java analogy, effectively a instance method definition). As qwertymik said,

Dog.prototype.woof = function(){ console.log( "Woof!" ); this.speak(); }

Then you'll be able to do

var foo = new Dog();
foo.woof();

Maybe you mean to do this:

Dog.prototype._super = Animal.prototype;
Dog.prototype.woof = function(){ console.log( "Woof!" ); this._super.speak(); }

//Rewrote the code to make it work

function Animal(){}
Animal.prototype.type = "animal";
Animal.prototype.speak = function(){ console.log( "I'm a " + this.type + 
    ". I can't really talk ;)" ); }

function Dog(){}
function F(){}

F.prototype = Object.create(Animal.prototype); //F inherits from animal
Dog.prototype = Object.create(F.prototype);    //Dog inherits from F

Dog.prototype.constructor = Dog; //resetting the constructor to Dog object
F.prototype.constructor=F;       // resetting the constrctor to F object 

Dog.prototype.type = "Dog";

Dog.prototype.woof = function(){ console.log( "Woof!" ); this.speak(); } //adding woof method to the prototype of dog

const rover = new Dog();

rover.woof();

// output
// Woof!
// I'm a Dog. I can't really talk ;)