Angular 2和Firebase。如何做独一无二的过滤？

npm install angularfire2 firebase --save

import { AngularFireModule } from 'angularfire2';
import { AngularFireDatabaseModule } from 'angularfire2/database';
import { AngularFireDatabase } from 'angularfire2/database';
import { Observable } from 'rxjs/Observable';

// Firebase配置
const firebaseConfig = {
  apiKey: 'YOUR_API_KEY',
  authDomain: 'YOUR_AUTH_DOMAIN',
  databaseURL: 'YOUR_DATABASE_URL',
  projectId: 'YOUR_PROJECT_ID',
  storageBucket: 'YOUR_STORAGE_BUCKET',
  messagingSenderId: 'YOUR_MESSAGING_SENDER_ID'
};

@NgModule({
  imports: [
    AngularFireModule.initializeApp(firebaseConfig),
    AngularFireDatabaseModule
  ],
  ...
})
export class AppModule { }

import { Component } from '@angular/core';
import { AngularFireDatabase } from 'angularfire2/database';
import { Observable } from 'rxjs/Observable';

@Component({
  selector: 'app-root',
  template: `
    <ul>
      <li *ngFor="let item of filteredItems | async">{{ item.name }}</li>
    </ul>
  `
})
export class AppComponent {
  filteredItems: Observable<any[]>;

  constructor(private db: AngularFireDatabase) {
    // 获取Firebase数据库中的数据
    const itemsRef = db.list('items');

    // 应用过滤器，只返回独一无二的数据
    this.filteredItems = itemsRef.valueChanges().map(items => {
      const uniqueItems = [];
      const uniqueNames = [];

      for (const item of items) {
        if (!uniqueNames.includes(item.name)) {
          uniqueItems.push(item);
          uniqueNames.push(item.name);
        }
      }

      return uniqueItems;
    });
  }
}