Not sure why, but when trying to chain constructors with call() or apply(), nothing happens.https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Function/call

i.e. extending the Point object :

function PointW( x, y, w ) {
	Point.call( this, x, y ); //call the Point constructor for this object

	this.weight = w; //set additional values
}
PointW.prototype = new Point(); //inherit Point methods/vars