toUpperCase str converts str to upper case using the locale-insensitive case mappings in the Unicode Character Database. Notice that the conversion can expand the number of letters in the result; for example the German ß capitalizes to two Ses in a row.toUpperCase "abc" = "ABC";;toUpperCase {js|Straße|js} = {js|STRASSE|js};;toLowerCase {js|πς|js} = {js|ΠΣ|js};;