问在dropdown中放置文本"select option“，然后清除Angular中的下拉列表

EN

 //templates/home/home.component.html

<select  [(ngModel)]='myselect' >
 <option [value]="" selected  >select and option</option>
 <option  *ngFor='let option of test' [value]="option.id">  
 {{option.nombre}}</option>
</select>

 //components/home/home.component.ts

 title = 'app';
 myselect:any;
 test:any= [{"id": "1", "nombre":"pedro" },{"id": "2", 
 "nombre":"yeison" }];
 ngOnInit() {
   this.timeoutFun();
 }

 timeoutFun() {
 setTimeout(function(){
 //clear my dropdown 
 this.myselect=""; 
 }, 5000);
}