To make a JavaScript class with a public method I'd do something like:

function Restaurant()
{
}

Restaurant.prototype.buy_food = function()
{
   // something here
}

Restaurant.prototype.use_restroom = function()
{
   // something here
}

That way users of my class can:

var restaurant = new Restaurant();
restaurant.buy_food();
restaurant.use_restroom();

How do I create a private method that my public buy_food and use_restroom methods can call but that users of the class can't call externally.

In other words, I want my method implementation to be able to do:

Restaurant.prototype.use_restroom = function()
{
   this.private_stuff();
}

But this shouldn't work:

var r = new Restaurant();
r.private_stuff();

How do I define private_stuff as a private method so both of those hold true?

I've read Doug Crockford's writeup a few times but it doesn't seem like "private" methods can be called by public methods and "privileged" methods can be called externally.