casecmp is a String class method in Ruby which is Case-insensitive version of String#<=>. For now, case-insensitivity only works on characters A-Z/a-z, not all of the Unicode characters. This method is different from casecmp! method.
Parameters: Here, str is the given string to be checked and other_str is the string to which str is compared.
Returns:This method will returns the true or false based on the equality of the str and other_str. It can also return nil if the two strings have incompatible encodings, or if other_str is not a string.