hidden classes

gistfile1.js

function Point(x, y) {
  this.x = x;
  this.y = y;
}

Point.prototype.addZ = function(val){
  this.z = val;
};

var p1 = new Point(11, 22);
var p2 = new Point(33, 44);
// At this point, p1 and p2 have a shared hidden class
p2.z = 55;
// warning! p1 and p2 now have different hidden classes!

// would this make them have different hidden classes as well?
p2.addZ(55);