Is there anyway to implement XOR in javascript

Question

I'm trying to implement XOR in javascript in the following way:

   // XOR validation
   if ((isEmptyString(firstStr) && !isEmptyString(secondStr)) ||
    (!isEmptyString(firstStr) && isEmptyString(secondStr))
   {
    alert(SOME_VALIDATION_MSG);
    return;
   }

Is there a better way to do this in javascript?

Thanks.

Answer 1

Checkout this explanation of different implementations of XOR in javascript.

Just to summarize a few of them right here:

if( ( isEmptyString(firstStr) || isEmptyString(secondStr)) && !( isEmptyString(firstStr) && isEmptyString(secondStr)) ) {
   alert(SOME_VALIDATION_MSG); 
   return; 
}

OR

if( isEmptyString(firstStr)? !isEmptyString(secondStr): isEmptyString(secondStr)) {
   alert(SOME_VALIDATION_MSG); 
   return;
}

OR

if( (isEmptyString(firstStr) ? 1 : 0 ) ^ (isEmptyString(secondStr) ? 1 : 0 ) ) {
   alert(SOME_VALIDATION_MSG); 
   return;
}

OR

if( !isEmptyString(firstStr)!= !isEmptyString(secondStr)) {
   alert(SOME_VALIDATION_MSG); 
   return;
}

Answer 2

You might be interested in this.

Answer 3

You are doing an XOR of boolean values which is easy to model into a bitwise XOR (which Javascript has):

var a = isEmptyString(firstStr) ? 1 : 0;
var b = isEmptyString(secondStr) ? 1 : 0;

if(a ^ b) { ... }

http://www.howtocreate.co.uk/xor.html

Answer 4

Hi

Javascript does not have a logical XOR operator, so your construct seems plausible. Had it been numbers then you could have used ^ i.e. bitwise XOR operator.

cheers

Answer 5

I pretend that you are looking for a logical XOR, as javascript already has a bitwise one (^) :)

I usually use a simple ternary operator (one of the rare times I use one):

if ((isEmptyString(firstStr) ? !isEmptyString(secondStr) 
                             : isEmptyString(secondStr))) {
alert(SOME_VALIDATION_MSG);
    return;
}

Edit:

working on the @Jeff Meatball Yang solution

if ((!isEmptyString(firstStr) ^ !isEmptyString(secondStr))) {
  alert(SOME_VALIDATION_MSG);
  return;
}

you negate the values in order to transform them in booleans and then apply the bitwise xor operator. Maybe it is not so maintainable as the first solution (or maybe I'm too accustomed to the first one)

Answer 6

You could use the bitwise XOR operator (^) directly:

if (isEmptyString(firstStr) ^ isEmptyString(secondStr)) {
  // ...
}

It will work for your example since the boolean true and false values are converted into 1 and 0 because the bitwise operators work with 32-bit integers.

That expression will return also either 0 or 1, and that value will be coerced back to Boolean by the if statement.

You should be aware of the type coercion that occurs with the above approach, if you are looking for good performance, I wouldn't recommend you to work with the bitwise operators, you could also make a simple function to do it using only Boolean logical operators:

function xor(x, y) {
  return (x || y) && !(x && y);
}


if (xor(isEmptyString(firstStr), isEmptyString(secondStr))) {
  // ...
}

Answer 7

XOR just means "are these two boolean values different?". Therefore:

if (!!isEmptyString(firstStr) != !!isEmptyString(secondStr)) {
    // ...
}

The !!s are just to guarantee that the != operator compares two genuine boolean values, since conceivably isEmptyString() returns something else (like null for false, or the string itself for true).

Answer 8

As others have pointed out, logical XOR is the same as not-equal for booleans, so you can do this:

  // XOR validation
  if( isEmptyString(firstStr) != isEmptyString(secondStr) )
    {
      alert(SOME_VALIDATION_MSG);
      return;
    }