isLetter
Determines if the specified character (Unicode code point) is a letter.
A character is considered to be a letter if its general category type, provided by getType(codePoint), is any of the following: UPPERCASE_LETTER, LOWERCASE_LETTER, TITLECASE_LETTER, MODIFIER_LETTER, or OTHER_LETTER.
Return
true if the character is a letter; false otherwise.
Since
1.5
Parameters
codePoint
the character (Unicode code point) to be tested.