lastIndexOf method Null safety
Returns the starting position of the last match pattern in this string,
searching backward starting at start, inclusive:
var string = 'Dartisans';
string.lastIndexOf('a'); // 6
string.lastIndexOf(RegExp(r'a(r|n)')); // 6
Returns -1 if pattern could not be found in this string.
string.lastIndexOf(RegExp(r'DART')); // -1
If start is omitted, search starts from the end of the string.
If supplied, start must be non-negative and not greater than length.
Implementation
int lastIndexOf(Pattern pattern, [int? start]);