Lazy Object via Proxy

LazyObjectViaProxy.js

//Create a Proxy for the lazy construction of an object
function buildLazyObject(constructorFn, ...args){
    let internalObject = null;
    //we don't care about the target, but compiler does not allow a null one, so let's pass an "empty object" {}
    return new Proxy({}, {
        get: function(target, property, receiver){
            console.log("this === receiver " + (this === receiver)); //false
            //"this" is not the proxy, but the handler object containing the traps (obviously are not the same object)
            internalObject = internalObject || (() => {
                console.log("Creating object");
                return new constructorFn(...args);
            })();
            
            //this way, if it's a method, internal calls to other methods of the class would go through the proxy also
            //for this case it makes no sense
            //return internalObject[property];
            
            let item = internalObject[property];
            if (typeof(item) === "function"){
                return function(...args){
                    return item.call(internalObject, ...args);
                };
            }
            else{
                return item;
            }
        },

        set: function(target, property, value, receiver){
            internalObject = internalObject || (() => {
                console.log("Creating object");
                return new constructorFn(...args);
            })();
            
            internalObject[property] = value;
        }
            
    });
}

//--------------------------------------------

class Person{
    constructor(name, age){
        this.name = name;
        this.age = age;
    }       

    sayHello(){
        return "Bonjour, Je suis " + this.name + " et j'ai " + this.age + ", ma ville est " + (this.city || "inconnu");
    }
}

let p1 = buildLazyObject(Person, "Francois", 2);
console.log("Proxy created");

console.log(p1.sayHello());

console.log("Second call");

console.log(p1.sayHello());

let p2 = buildLazyObject(Person, "Didier", 4);
console.log("Proxy created");
p2.city = "Marseille";
console.log("after set value");

console.log(p2.sayHello());

// Proxy created
// this === receiver false
// Creating object
// Bonjour, Je suis Francois et j'ai 2, ma ville est inconnu
// Second call
// this === receiver false
// Bonjour, Je suis Francois et j'ai 2, ma ville est inconnu
// Proxy created
// Creating object
// after set value
// this === receiver false
// Bonjour, Je suis Didier et j'ai 4, ma ville est Marseille