bytesCount method
Calculates the byte count of a string, treating non-ASCII characters as 2 bytes.
This is often used for validation where systems have byte-based length limits (e.g., some database varchar fields).
Example:
'你好'.bytesCount(); // 4
'hello你好'.bytesCount( ) ; // 9
Implementation
int bytesCount() {
return this.replaceAll(RegExp(r"[^\u0000-\u00ff]"), "aa").length;
}