Completion values in JavaScript

Paul Irish tweeted a while back a code snippet that puzzled him (and me).

> "omg"; var x = 4;
// "omg"

> eval( `"omg"; var x = 4;` );
// "omg"

We both expected that the "return value" of this lines will be undefined. It turns out what we see after evaluating these lines in a JavaScript console are not return values but rather a statement completion values. If you want to dig deeper in this topic Matt Zeunert enlightened me with his article.