Isolates and message-owned work

The idea

Async and await let an isolate continue other event-loop work while an operation waits; they do not automatically move a CPU-heavy loop to another isolate. A long synchronous computation can still delay responsiveness. Isolates provide separate execution contexts with their own mutable state, communicating through messages instead of sharing ordinary mutable objects.

For suitable native Dart environments, Isolate.run can execute a computation elsewhere and return its result through a Future. Inputs and results must satisfy the relevant message-transfer rules. Keep transferred data focused and avoid accidentally capturing a large object graph in a closure. Measure communication overhead as well as compute time, because moving a tiny operation can cost more than performing it locally.

import "dart:isolate";
Future<void> main() async {
  final total=await Isolate.run(() => [2,3,5].fold<int>(0,(a,b)=>a+b));
  print(total);
}

10

The example requires an environment supporting dart:isolate; it is not a promise of execution in every browser editor.