What are extensions in Dart used for?

Extensions in Dart allow adding functionality to existing classes without modifying their source code. This is useful for:

• Adding utility methods to standard data types (String, int, List, etc.).
• Extending classes from third-party libraries without modifying them.
• Improving code readability and organizing logic related to a specific type.

Example:

extension StringUtils on String {
  String capitalize() {
    if (isEmpty) return this;
    return this[0].toUpperCase() + substring(1);
  }
}

void main() {
  String text = "привет мир";
  print(text.capitalize()); // Outputs: Привет мир
}