Is !0 and !1 something more than a shorthand for true/false? [duplicate]

Question

Reading through some code, I came across the use of !0 and !1. I realize that these are shorter ways of writing true and false.

!0 === true
!1 === false

This of course save a few bytes, but is there some other reason to use it?

Is there a name for this way of writing it?

Curler

Yes - "confusing and lacking readability" ;) – Philip

I prefer !!0 (false) and !!1 (true) for much more clarity and only a 50% size increase! No. Really, use the keywords .. – Ciri

@pst Thanks for that, makes much more sense. !0 being true is really easy to misread. – Curler

If you want to know how affects performance, go to jsperf.com/checking-if-true-or-false and run the tests – Curson

Answer 1

Most JavaScript minification tools, like UglifyJS, generate that code because it's shorter and semantically equivalent. For example, given:

var x = true;
if (x) { 
  alert(x); 
}

UglifyJS will generate var x=!0;x&&alert(x).

Usually, you don't need to write code using that style; let the minifiers do their work :-).

Kinaesthesia

Thanks! I sensed it was the work of a minifier, just wanted to make sure there wasn't something more to it that I was missing. – Curler