null的含义是什么！在TypeScript中？

Question

我在Angular的源代码中多次看到null !。以下!标记的含义是什么？

示例：

• https://github.com/angular/angular/blob/master/packages/router/src/router.ts#L221

  private navigations = new BehaviorSubject<NavigationParams>(null !);
  

• https://github.com/angular/angular/blob/master/packages/router/src/router.ts#L357

  this.locationSubscription = null !;