The W3C wisely explains, "In other situations, such as for APIs, UTF-16 or UTF-32 may be more appropriate.
使用增補字符時,對於一個增補字符,使用CODEUNITS16 計算是兩個UTF-16代碼單元,而使用CODEUNITS32 計算則是一個UTF-32代碼單元。
When supplementary characters are involved, a supplementary is counted as two UTF-16 code units using CODEUNITS16, or one UTF-32 code unit using CODEUNITS32.