+ 2

what does " !! "mean in this code ? and what does the first if statement mean?

var num = 20; if ( !! num || ! num && num - num){ console.log("A"); } else if (num == 20) { console.log("C") } else { console.log("B"); }

14th Feb 2020, 12:30 AM
Marina Khamis
Marina Khamis  - avatar
3 ответов
+ 4
! = NOT ! true = false ! false = true !! = NOT NOT !! true = true !! false = false !!! true = false !!! false = true https://medium.com/@edplatomail/js-double-bang-or-the-not-operator-part-40e55d089bf0 !! num returns true. ! num returns false || OR (true || true = true, false || true = true, true || false = true) && AND (only true for true && true) if(true OR false && 0) false AND 0 returns false true || false returns true -> the whole condition in if statement is true output: A But don't ask me about the sense of such a condition ;) Edit: Maybe it is just an exercise about boolean
14th Feb 2020, 1:03 AM
Denise Roßberg
Denise Roßberg - avatar
+ 6
!!X === !(!X) === Boolean(X) !X === !(Boolean(X)) For me the first if statement has not meaning.
14th Feb 2020, 12:53 AM
Kevin ★
+ 2
A trick to convert a number to its boolean form.
14th Feb 2020, 1:06 AM
Sonic
Sonic - avatar