How to get the key in Update() of Firebase record in Angular

Question

Hy Friends,

 

I'm developing CRUD application with Angular using Firebase database. I've already seen many tutorials and articles, but it doesn't make any sense to me. Most of them defining a Model class with key attribute. But in my case, I've defined the firebase schema

 

Here 1 is the key and course1 is the value. My component code is

export class AppComponent {
  courses$;
  course: AngularFireList;

  constructor(private db: AngularFireDatabase) {
    this.courses$ = db.list('/courses').valueChanges();
  }

  add(course: HTMLInputElement) {
    if (!this.course) {
      this.course = this.getData();
    }
    this.course.push({
      name: course.value,
      price: 150,
      isLive: true,
      sections: [
        { title: 'Component'},
        { title: 'Service'},
        { title: 'Template'}
      ]
    });
    course.value = '';
  }

  getData() {
    return this.db.list('/courses');
  }

  update(course) {
    console.log(course);
  }
}

And my html template code is

<input type="text" (keyup.enter)="add(course)" #course>
<ul>
  <li *ngFor="let course of courses$ | async">
    {{ course.name || course }}
    <button (click)="update(course)">Update</button>
  </li>
</ul>

Problem: How can I update and delete firebase record with Angular. I need update() and delete() method code of Angular 4+. Bundle of thanks in advance.