behaviors.js

// Let's specify some Behaviors, first

// Gotta have x,y coords!
var Positionable =
{ x: 0
, y: 0   // phear my inverted c0mmaZ!
};

// Mmmm, delicious physics
var Physical =
{ speedX: 0
, speedY: 0
, tick: function()
  {
    this.x += this.speedX;
    this.y += this.speedY;
  }
};

// Annnnnnnd let's draw this thing, too
var Renderable =
{ render: function(gc)
  {
    gc.fillStyle = 'rgb(255,0,0)';
    gc.fillRect( this.x-5, this.y-5, 10, 10 );
  }
}

// Build a GameObject using these behaviors
var gameObject = GameObject.create();

gameObject.actsLikeA(Positionable);
gameObject.x = Math.random()*800;   // Magic numbers ftl, but whatev
gameObject.y = Math.random()*600;

gameObject.actsLikeA(Physical);
gameObject.speedX = Math.random()*10 - 5;
gameObject.speedY = Math.random()*10 - 5;

gameObject.actsLikeA(Renderable);

// Now we can be like:
gameObject.tick();
gameObject.render(graphicsContext);
// ... in the game loop. Simple!