onlyNumbers method
Extracts only digit characters, removing everything else.
The removeSpaces parameter is accepted for API consistency but currently unused.
Example:
'(123)-456-7890'.onlyNumbers() // '1234567890'
'abc123def456'.onlyNumbers() // '123456'
'no digits here'.onlyNumbers() // ''
Implementation
String onlyNumbers([bool removeSpaces = false]) {
String result = replaceAll(RegExp(r'[^0-9]'), '');
return removeSpaces ? result.replaceAll(RegExp(r'\s+'), '') : result;
}