Except it's also likely, perhaps more so, that `this.finished` is `undefined`, which results in fundamentally the same problem but in the opposite direction of truthiness.

In which case I still see it as just a personal preference. The prefix of "is" becomes reassurance that something is intended to have a boolean value, which may be more important.

Of course it goes without saying that both of these things are (usually) addressed by a system like Typescript.