simplify negated existence compilation

[michaelficarra]

A minor optimization:

• !a?
  • currently compiles to: !(typeof a != "undefined" && a != null);
  • should compile to: typeof a == "undefined" || a == null;
• !a.b?
  • currently compiles to: !(a.b != null);
  • should compile to: a.b == null;

[dvv]

I believe to (typeof a == "undefined" || a == null) and (a.b == null), notice the braces

[michaelficarra]

@dvv: Depending on the situation, possibly. But the compiler will handle that for us.

[jrus]

Yes, I was a bit puzzled that these two behave differently:

foo unless a?
foo if not a?

Namely:

if (typeof a == "undefined" || a === null) {
  foo;
}
if (!(typeof a != "undefined" && a !== null)) {
  foo;
}

[michaelficarra]

@jrus: They don't behave differently, but they do (unfortunately) compile differently.

[jrus]

Yeah, I meant the compiler behaves differently, not that the output behaves differently. Silly ambiguous English. :)

[vendethiel]

Seems to work that way.