# scheduleMicrotask function

void scheduleMicrotask (void callback())

Runs a function asynchronously.

Callbacks registered through this function are always executed in order and are guaranteed to run before other asynchronous events (like Timer events, or DOM events).

Warning: it is possible to starve the DOM by registering asynchronous callbacks through this method. For example the following program runs the callbacks without ever giving the Timer callback a chance to execute:

    main() {
      Timer.run(() { print("executed"); });  // Will never be executed.
      foo() {
        scheduleMicrotask(foo);  // Schedules [foo] in front of other events.
      }
      foo();
    }

## Other resources

- The Event Loop and Dart: Learn how Dart handles the event queue and microtask queue, so you can write better asynchronous code with fewer surprises.

## Implementation

    void scheduleMicrotask(void callback()) {
      _Zone currentZone = Zone.current;
      if (identical(_rootZone, currentZone)) {
        // No need to bind the callback. We know that the root's scheduleMicrotask
        // will be invoked in the root zone.
        _rootScheduleMicrotask(null, null, _rootZone, callback);
        return;
      }
      _ZoneFunction implementation = currentZone._scheduleMicrotask;
      if (identical(_rootZone, implementation.zone) &&
          _rootZone.inSameErrorZone(currentZone)) {
        _rootScheduleMicrotask(
            null, null, currentZone, currentZone.registerCallback(callback));
        return;
      }
      Zone.current.scheduleMicrotask(Zone.current.bindCallbackGuarded(callback));
    }