README
altERnaTIng cAsE <=> ALTerNAtiNG CaSe
Define String.prototype.toAlternatingCase (or a similar function/method such as to_alternating_case/toAlternatingCase/ToAlternatingCase in your selected language; see the initial solution for details) such that each lowercase letter becomes uppercase and each uppercase letter becomes lowercase. For example:
> "hello world".toAlternatingCase() === "HELLO WORLD"
>
> "HELLO WORLD".toAlternatingCase() === "hello world"
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> "hello WORLD".toAlternatingCase() === "HELLO world"
>
> "HeLLo WoRLD".toAlternatingCase() === "hEllO wOrld"
>
> "12345".toAlternatingCase() === "12345" // Non-alphabetical characters are unaffected
>
> "1a2b3c4d5e".toAlternatingCase() === "1A2B3C4D5E"
>
> "String.prototype.toAlternatingCase".toAlternatingCase() === "sTRING.PROTOTYPE.TOaLTERNATINGcASE"
As usual, your function/method should be pure, i.e. it should not mutate the original string.