pub fn len(s: string, i: option<number>, j: option<number>) -> option<number>Expand description
Returns the number of UTF-8 characters in string s that start
between byte positions i and j (default 1 and −1). If it finds
any invalid byte sequence, returns nil plus the position of the
first invalid byte.
§Examples
print(utf8.len("héllo")) --> 5
print(#"héllo") --> 6 (é takes two bytes)
print(utf8.len("\xFF")) --> nil 1 (invalid byte at position 1)