js inheritance

test.js

var extend = function(child, parent) {
  for (var key in parent) {
    if(parent.hasOwnProperty(key)) child[key] = parent[key];
  }

  function ctor() {
    this.constructor = child;
  }
  
  ctor.prototype = parent.prototype;
  child.prototype = new ctor();
  child.__super__ = parent.prototype;

  return child;
};

function Animal(name) {
  this.name = name;
}

Animal.prototype.move = function(meters) {
  return console.log(this.name + (" moved " + meters + "m."));
};

extend(Snake, Animal);

function Snake() {
  return Snake.__super__.constructor.apply(this, arguments);
}

Snake.prototype.move = function() {
  console.log('Slithering...');
  return Snake.__super__.move.call(this, 23);
};

var sam = new Snake('Sam');

sam.move();

вот оно какое, наследование в js..