truncate method
Truncates a String with more than length characters.
length must be more than 0.
If length > String.length the same String is returned without truncation.
Example
String f = 'congratulations';
String truncated = f.truncate(3); // Returns 'con...'
Implementation
String? truncate(int length) {
if (this == null) return null;
if (this!.isEmpty) return this;
if (length <= 0) return this;
if (length > this!.length) return this;
return '${this!.substring(0, length)}...';
}