// Dart
String name = "John";
int? age; // Nullable int

// TypeScript
let name: string = "John";
let age: number | null = null;

// Dart
var name = "John";        // Type inferred
final userId = getUserId(); // Runtime constant
const apiUrl = "https://..."; // Compile-time constant

// JavaScript
let name = "John";
const userId = getUserId();
const apiUrl = "https://...";

// Dart
void greet(String name) => print('Hello $name');
Function callback = () => print('Done');

// JavaScript
const greet = (name) => console.log(`Hello ${name}`);
const callback = () => console.log('Done');

// Dart
abstract class Shape {
  double area();
}

class Rectangle extends Shape with Printable {
  final double width, height;
  
  Rectangle(this.width, this.height);
  
  @override
  double area() => width * height;
}

// TypeScript
abstract class Shape {
  abstract area(): number;
}

class Rectangle extends Shape {
  constructor(private width: number, private height: number) {}
  
  area(): number {
    return this.width * this.height;
  }
}

// Dart
Future<String> fetchData() async {
  final response = await http.get(Uri.parse(url));
  return response.body;
}

// JavaScript
async function fetchData() {
  const response = await fetch(url);
  return response.text();
}

// Dart
List<String> names = ['Alice', 'Bob'];
Map<String, int> ages = {'Alice': 30, 'Bob': 25};
Set<String> uniqueNames = {'Alice', 'Bob'};

// JavaScript
const names = ['Alice', 'Bob'];
const ages = {'Alice': 30, 'Bob': 25};
const uniqueNames = new Set(['Alice', 'Bob']);

// Dart
String name = "John";
String message = 'Hello $name, you have ${messages.length} messages';

// JavaScript
const name = "John";
const message = `Hello ${name}, you have ${messages.length} messages`;

// Dart
try {
  final result = await riskyOperation();
} on NetworkException catch (e) {
  print('Network error: ${e.message}');
} catch (e) {
  print('Unknown error: $e');
} finally {
  cleanup();
}