compfinal typehead

import { Component, OnInit } from '@angular/core';

import {Subject} from 'rxjs/Subject';
import {Observable} from 'Rxjs/Rx';
import { AngularFirestore } from 'angularfire2/firestore';


@Component({
  selector: 'app-root',
  templateUrls:''
})
export class AppComponent implements OnInit {
  searchterm: string;

  startAt = new Subject();
  endAt = new Subject();

  startObs = this.startAt.asObservable();
  endObs = this.endAt.asObservable();

  names;

  public data: Observable<any[]>;

  constructor(private db: AngularFirestore) {
    // this.data = db.collection('/data').valueChanges();
  }

  ngOnInit(){
    Observable.combineLatest(this.startObs, this.endObs).subscribe((value) => {
      this.firequery(value[0], value[1]).subscribe((names) => {this.names = names;
    })
    })
  }

  search($event){
    let q = $event.target.value;
    this.startAt.next(q);
    this.endAt.next(q + "\uf8ff");
  }

  firequery(start, end){
    return this.db.collection('data', ref => ref.limit(4).orderBy('name').startAt(start).endAt(end)).valueChanges();
  };
}