Converts Object
to boolean
. If it was falsey (e.g. 0
, null
, undefined
, etc.), it will be false
, otherwise, true
.
!object // inverted boolean
!!object // non inverted boolean so true boolean representation
So !!
is not an operator, it’s just the !
operator twice.
It may be simpler to do:
Boolean(object) // boolean
Real World Example “Test IE version”:
const isIE8 = !! navigator.userAgent.match(/MSIE 8.0/);
console.log(isIE8); // returns true or false
If you ⇒
console.log(navigator.userAgent.match(/MSIE 8.0/));
// returns either an Array or null
But if you ⇒
console.log(!!navigator.userAgent.match(/MSIE 8.0/));
// returns either true or false