JavaScript traces its ancestry back to C, and C does not have a logical XOR operator. Mainly because it's not useful. Bitwise XOR is extremely useful, but in all my years of programming I have never needed a logical XOR.
If you have two boolean variables you can mimic XOR with:
if (a != b)
With two arbitrary variables you could use !
to coerce them to boolean values and then use the same trick:
if (!a != !b)
That's pretty obscure though and would certainly deserve a comment. Indeed, you could even use the bitwise XOR operator at this point, though this would be far too clever for my taste:
if (!a ^ !b)
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