Question

Coffeescript code:

class Animal
  constructor: (@name) ->

  move: (meters) ->
    alert @name + " moved #{meters}m."

class Snake extends Animal
  move: ->
    alert "Slithering..."
    super 5

alert Snake instanceof Animal

Here is a link.

I really think this result true.
And my reason is this __extends method in compiled JavaScript:

__extends = function (child, parent) {
    for(var key in parent) {
        if(__hasProp.call(parent, key)) child[key] = parent[key];
    }function ctor() {
        this.constructor = child;
    }
    ctor.prototype = parent.prototype;
    child.prototype = new ctor();
    child.__super__ = parent.prototype;
    return child;
};

child.prototype.prototype is parent.

Can someone tell me why?
And I know below is true:

alert new Snake('a') instanceof Animal

Answer 1

Your Snake is a subclass of Animal:

class Snake extends Animal

That means that Snake (a “class”) is actually an instance of Function, not Animal. A Snake object, on the other hand, would be an instance of Animal:

alert Snake instanceof Function     # true
alert (new Snake) instanceof Animal # true

And if you try to get a Snake instance to move:

(new Snake('Pancakes')).move()

you’ll see that the right methods are called.

Demo: http://jsfiddle.net/ambiguous/3NmCZ/1/