Method cancelTask

packages/zone.js/lib/zone-impl.ts:1053–1080

(task: Task)

    }

    cancelTask(task: Task): any {
      if (task.zone != this)
        throw new Error(
          'A task can only be cancelled in the zone of creation! (Creation: ' +
            (task.zone || NO_ZONE).name +
            '; Execution: ' +
            this.name +
            ')',
        );

      if (task.state !== scheduled && task.state !== running) {
        return;
      }

      (task as ZoneTask<any>)._transitionTo(canceling, scheduled, running);
      try {
        this._zoneDelegate.cancelTask(this, task);
      } catch (err) {
        // if error occurs when cancelTask, transit the state to unknown
        (task as ZoneTask<any>)._transitionTo(unknown, canceling);
        this._zoneDelegate.handleError(this, err);
        throw err;
      }
      this._updateTaskCount(task as ZoneTask<any>, -1);
      (task as ZoneTask<any>)._transitionTo(notScheduled, canceling);
      task.runCount = -1;
      return task;
    }

    private _updateTaskCount(task: ZoneTask<any>, count: number) {
      const zoneDelegates = task._zoneDelegates!;