compiled.js

var A = function() {};

A.prototype.over = function() {};

var B = function() {
  this.where_am_i = 'at work';
  A.call(this);
};

var _fn = function() {};
_fn.prototype = B.prototype;
B.prototype = new _fn();

B.prototype.sayWhereYouAre = function sayWereYouAre() {
  alert('I am ' + this.where_am_i);
};

B.prototype.over = function over() {
  A.prototype.over.call(this);
};

oo.coffee

prototype A
  over: ->
    super()

prototype B extends A
 
  constructor: ->
    @where_am_i: 'at work'
    super()
 
  sayWhereYouAre: ->
    alert 'I am ' + @where_am_i

  over: ->
    super()