Using the (!!!) operator in JavaScript? [duplicate]

One ! would be enough :)

!1 // false
!0 // true

!! is not an operator in itself; it is merely a way of using JavaScript's logical NOT (!) operator.

To convert x to a boolean, !!x works because when you negate a boolean twice, you get the original boolean, and !x converts x to a boolean before negating it.

Likewise, !!!x converts x to a boolean and negates it three times, which is equivalent to negating it only once. So you can use !x instead of !!!x.

that's for "True" conditions.

No, it's for any value. !! will convert any value in it's equivalent Boolean value.

Why? Because the not operator simply returns the opposite Boolean value. So

0    // is falsy
!0   // -> true
!!0  // -> false

'foo'    // is truthy
!'foo'   // -> false
!!'foo'  // -> true

Any additional application will just toggle the value again. Thus !!! is equivalent to ! and !!!! is equivalent to !! and so on.

var boolCheck = 0;
   boolCheck //0
  !boolCheck //true
 !!boolCheck //false
!!!boolCheck //true - again

Same thing here:

var boolCheck = 1;
   boolCheck //1
  !boolCheck //false
 !!boolCheck //true
!!!boolCheck //false - again

There is no reason to use this ( !!! ), it is a tautology. !! is useful when:

1. we need to have a Boolean value, when there are some results ( !!5 => true );
2. we need to shorten false with !1 or true - !0.
   1. or to skip the wrapper.

This answers your question perfectly https://stackoverflow.com/a/264037/1561922

!!!x is probably inversing a boolean conversion !!x:

var myBool = Boolean("false");  // == true

var myBool = !!"false";  // == true

"Any string which isn't empty will evaluate to true"

So !!!"false"; // == false

This question is NOT a joke. Node.js (downloaded 5 days ago) uses this in Assert.js for example:

function ok(value, message) {
  if (!!!value) fail(value, true, message, '==', assert.ok);
}
assert.ok = ok;

EDIT: I think they did it for code readability reasons out of habit, because !value already suffices.

EDIT: Node changed it. I have no idea why my version of Node.js that was downloaded 5 days ago is still with the !!!value instead of the !value in GitHub.

EDIT: This is the reason why.