Shorthand for flipping a boolean variable

Question

How can I flip the value of a boolean variable in javascript, without having to include the variable name twice? So

foobarthings[foothing][barthing] = !foobarthings[foothing][barthing];

without writing foobarthings[foothing][barthing] twice.

Strange, considering `foo++` exists. Couldn't there be `foo!!` or something? — yellow-saint, Apr 15 '15 at 08:36

score 32 · Accepted Answer · answered Dec 20 '12 at 13:08

32

There is no shorter way than what you currently have.

answered Dec 20 '12 at 13:08

alex

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that's not entirely true, there is such thing as the `not` operator: `ver inverse = return !foo;` that's completely valid – J-Cake Jul 13 '18 at 03:32
2

@JacobSchneider The code you posted isn't syntactically valid and the OP already demonstrates knowledge of the `!` operator. – alex Jul 13 '18 at 12:10
Anujith Answered with `^=` operation, why do you think that's not valid? – Pixsa Jan 06 '23 at 19:50

score 13 · Answer 2 · answered Dec 20 '12 at 13:21

13

You can do this:

foo ^= 1

But this really switches foo between 0 and 1, not true and false.

answered Dec 20 '12 at 13:21

Sjoerd

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but then you can do `(foo ^= 1) == true` (must be `==` **not** `===`) – J-Cake Jul 13 '18 at 03:33

score 3 · Answer 3 · answered Dec 20 '12 at 13:20

3

var value = true;
alert(value);
value ^= true;
alert(value);

You could get 1 or 0 here

answered Dec 20 '12 at 13:20

Anujith

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Could this be considered *short hand*? – alex Dec 20 '12 at 13:22

score 0 · Answer 4 · answered Nov 04 '22 at 02:27

you can create a new constructor with a boolean property and then add a prototype to flip that

function Bit(bit=false) {
  this._ = bit;
}
Bit.prototype.flip = function() {
  this._ = !this._;
  return this._
}

//example:
var foo = new Bit();
console.log(foo._) //logs false
foo.flip() //flips to true
console.log(foo._); //logs true
console.log(foo.flip()) //flips to false and logs it

J-Cake · Answer 5 · 2018-07-14T13:51:29.127

-1

To flip the value of a boolean variable in JS you need the syntax like this:

return !foo;

It's really that easy...

Or you can do (foo ^= 1) == true (must be == not ===)

edited Jul 14 '18 at 13:51

answered Aug 15 '17 at 14:39

J-Cake

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The question is about avoiding repeating the name when doing assignment and flipping the boolean state. – alex Jul 13 '18 at 12:12
I only use the variable's name once – J-Cake Jul 14 '18 at 13:51
2

The user want's to assign the flipped value back to the same variable name, which this answer does not cover. – alex Jul 15 '18 at 20:00

score -3 · Answer 6 · answered Dec 20 '12 at 13:13

-3

You can have just foo and !foo in the place where you execute it or check the condition.

answered Dec 20 '12 at 13:13

Arunkumar Srisailapathi

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No, I need to store the opposite value in it. – chtenb Dec 20 '12 at 13:13

Shorthand for flipping a boolean variable

6 Answers6

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