<select name="city" id="city" [(ngModel)] = "config.cityCode" (change)="filterList()">
   <option [value]="city.value" *ngFor="let city of citylist" >{{city.name}}</option>
  </select>
  <select name="type" id="type" [(ngModel)] = "config.areaType" (change)="filterList()">
   <option value="">全部</option>
   <option value="TRAFFIC">交通</option>
   <option value="TRAVEL">旅游</option>
  </select>
  <input type="text" class="search" id="search" 
    [(ngModel)] = "config.name" 
    (input)="filterList()"
    placeholder="请输入关键字">

 // 用于传递配置项
 public $filter = new Subject<any>();
 // 过滤条件
 public config: FilterConfig = {
 cityCode : '',
 areaType : '',
 name : ''
 };
 ngOnInit() {
 // 监听过滤配置项
 this.$filter.pipe(
  debounceTime(500),
  distinctUntilChanged( (n: FilterConfig , o: FilterConfig): boolean => {
  return n.name === o.name &&
    n.cityCode === o.cityCode &&
    n.areaType === o.areaType;
  })
 ).subscribe( _config => {
  this.getRegionList(_config);
 });
 }
 filterList() {
 // 每次都要发送一个新的对象，否则distinctUntilChanged compare的时候会一直比较同一个对象的值
 this.$filter.next(Object.assign({}, this.config));
 }
 getRegionList (_config) {
 // 发送请求，更新区域数据
 console.log(_config);
 }