Creating JavaScript proxies that can be modified (replace the get trap logic)

modifiableProxy.js

function modifiableProxyFactory(target){
	//initialize the proxy with a "transparent" trap
	let coreGetTrapFunc = (target, property, receiver) => target[property];
	let handler = {
		//the "get trap" checks if we want to set the trap, otherwise it invokes the existing trap
		get: function(target, property, receiver){
			if (property === "setGetTrap"){
				console.log("setting a new get trap!");
				return function(getTrap){
					coreGetTrapFunc = getTrap;
				};
			}
			else{
				return coreGetTrapFunc(target, property, receiver);
			}
		}
	};
	return new Proxy(target, handler);
}

//let's test it:

class Person{
	constructor(name){
		this.name = name;
	}
	
	sayHi(){
		return "Hello I'm " + this.name;
	}	
}
 
let p2 = new Person("Emmanuel");
console.log(p2.sayHi());

let proxiedP2 = modifiableProxyFactory(p2);
console.log("\n- After creating 'empty' proxiedP2");
console.log(proxiedP2.sayHi() + "\n");


//------------------------------------
proxiedP2.setGetTrap(function(target, property, receiver){
	let it = target[property];
	if (typeof it != "function"){
		return it;
	}
	else{
		return function(){
			console.log(property + " called");
			return it.call(this, ...arguments);
		}
	}
});

console.log("\n- After reassigning get trap");
console.log(proxiedP2.sayHi() + "\n");


//------------------------------------
proxiedP2.setGetTrap(function(target, property, receiver){
	let it = target[property];
	if (typeof it != "function"){
		return it;
	}
	else{
		return function(){
			console.log(property + " CALLED!!!");
			return it.call(this, ...arguments);
		}
	}
});

console.log("\n- After reassigning get trap again");
console.log(proxiedP2.sayHi() + "\n");


//-- output:

// Hello I'm Emmanuel

// - After creating 'empty' proxiedP2
// Hello I'm Emmanuel

// setting a new get trap!

// - After reassigning get trap
// sayHi called
// Hello I'm Emmanuel

// setting a new get trap!

// - After reassigning get trap again
// sayHi CALLED!!!
// Hello I'm Emmanuel