It's now possible if your browser has support for the ES6 Proxy feature. You can check this in the ECMAScript 6 compatibility table.
If you have the proxy support, you would use it as follows:
let handler = {
get(target, name) {
return `Value for attribute ${name}`
}
}
let x = new Proxy({}, handler);
console.log(x.lskdjoau); // produces message: "Value of attribute 'lskdjoau'"
Works in chrome, firefox, and node.js. Downsides: doesn't work in IE - freakin IE. Soon.