JSFiddle - React, Tailwind, and code Playground

JavaScript

var user = {
    name: "Vasya",
	family: "Pupkin"
}

Object.defineProperty(user, "fullLength", {
    get: function(){
		var result = "";
		for(var key in user){
			result = result + user[key]
		}
		return result.length
	}

})



alert("в объекте user " + user.fullLength + " символов");//11
user.test = "ok"
alert("в объекте user " + user.fullLength + " символов"); //13