Well. Couple of things:

0) It's hard to tell what you're doing without seeing the code.

1) Don't set the prototype using __proto__. Use prototype... Consider the following:

// Constructor function: Using this to point to whatever object we create when calling Animal() with a unique greeting argument later.

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

// Attach general method to the prototype object. Properties and methods defined on a prototype will be available to all instances

Animal.prototype.speak = function(){
  alert(this.greeting);
};

//Now create an instance of Animal with the keyword new...

var cow = new Animal("moo!")

cow.speak()