protopattern.js

var X = function () {
  return new X.prototype.init() ;
};

X.prototype = {
  init: function () {
    this.y = 0;

    return this;
  }, 
  y: 1
}; 

X.prototype.init.prototype = X.prototype;
X.prototype.y = 1;


console.log(X());
console.log(X.y); //undefined

console.log(X().y);