superclass

superclass.js

// Removed toJSON, just for beautifying :)


/* CONSTRUCTOR -> */ function expression() {

};

Object.defineProperty(expression.prototype, "_type", 
      				{
						get : function(){
							return Object.getPrototypeOf(this).constructor.name;
						}
					});
                              
/* CONSTRUCTOR -> */  function lambdaExpression() {

};

// Here you change the prototype of lambdaExpression, which is alright
lambdaExpression.prototype = Object.create(expression.prototype);

// But you need to set the constructor of lambdaExpression to be lambdaExpression
lambdaExpression.prototype.constructor = lambdaExpression;


/* CONSTRUCTOR -> */ function lambda3x1(body, tailCall, parameters) {
      this.body = body;
      this.tailCall = tailCall;
      this.parameters = parameters;
};

lambda3x1.prototype = Object.create(lambdaExpression.prototype);
lambda3x1.prototype.constructor = lambda3x1;

// Create new lambda3x1, the new keyword is important
var lam = new lambda3x1("body", "tail", "params");

// get the prototype of lam, which is expression
var lamPrototype = Object.getPrototypeOf(lam);
// get the constructor - which the function decleration look at the comments ^
// which will return a Function, and get it's name
console.log(lamPrototype.constructor.name);

console.log(lam._type);

// DETAILS DOCUMENTATION - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/create