Edit in JSFiddle

let handler = {
	get: function(target, name) {
  	return name in target ? target[name] : "Key does not exist";
  }
}

let obj = {
  c: "car",
  b: "bike"
};

let proxyObj = new Proxy(obj, handler);

document.write(proxyObj.b, "<br>"); //Result -> "bike"
document.write(proxyObj.c, "<br>"); //Result -> "car"
document.write(proxyObj.l); //Result -> "Key does not exist"