超级原型继承

Question

I am not sure what the right way to handle a "super" object in prototypal inheritance (as described by Douglas Crockford) should be. Currently I am using this.__proto__ , which leads to weird behavior when creating new objects. Here is a simple example.

var Animal = { talk: function() { return "I am an animal"}}
var Cat = Object.create(Animal);                            
Cat.talk = function(){return "I am a cat. " + this.__proto__.talk()}; 
var myCat = Object.create(Cat)
console.log(myCat.talk());

What I want the final output to be is "I am a cat. I am an animal." Instead what I get is "I am a cat. I am a cat. I am an animal.". This makes perfect sense since the prototype of myCat is Cat, not animal!

How do I deal with this behavior to replicate the inheritance from other languages that I know and love?

Update 1/5/2015 I gave up on prototypal inheritance. One of these days I'll just switch to typescript I think...

Answer 1

You should call the Animal's talk function, but pass your cat in for the thisArg :

Animal.talk.call( this );

All together:

var Animal = { talk: function() { return "I am an animal"}}
var Cat = Object.create(Animal);                            
Cat.talk = function(){return "I am a cat. " + Animal.talk.call( this )}; 
var myCat = Object.create(Cat)
console.log(myCat.talk());

Answer 2

you will need explicitly mention Animal as Cat 's parent

var Animal = { talk: function() { return "I am an animal"}}
var Cat = Object.create(Animal);           
Cat.parent = Animal;    //so that you can invoke its method later
Cat.talk = function(){return "I am a cat. " + this.parent.talk.call(this)}; 
var myCat = Object.create(Cat);

Other than this I don't see how you will do this without specifically referring Animal class while defining Cat.talk .