Here is the textbook standard way of describing a 'class' or constructor function in JavaScript, straight from the Definitive Guide to JavaScript:

function Rectangle(w,h) {
    this.width = w;
    this.height = h;
}
Rectangle.prototype.area = function() { 
    return this.width * this.height;
};

I don't like the dangling prototype manipulation here, so I was trying to think of a way to encapsulate the function definition for area inside the constructor. I came up with this, which I did not expect to work:

function Rectangle(w,h) {
    this.width = w;
    this.height = h;
    this.constructor.prototype.area = function() { 
        return this.width * this.height;
    };
}

I didn't expect this to work because the this reference inside the area function should be pointing to the area function itself, so I wouldn't have access to width and height from this. But it turns out I do!

var rect = new Rectangle(2,3);
var area = rect.area(); // great scott! it is 6

Some further testing confirmed that the this reference inside the area function actually was a reference to the object under construction, not the area function itself.

function Rectangle(w,h) {
    this.width = w;
    this.height = h;
    var me = this;
    this.constructor.prototype.whatever = function() { 
        if (this === me) { alert ('this is not what you think');}
    };
}

Turns out the alert pops up, and this is exactly the object under construction. So what is going on here? Why is this not the this I expect it to be?