title: how to reset select in angular2
body: <p>I have tow select lists (select1 and select2) in my form, select2 depends on select2 selection, when select1 selection change options in select2 must be change this work fine but my problem is that on change don't return to default option, it gives me last index of last select2 selection,
  i want on change the select2 option change and index of selected option return to 0 or default option
  I am using ng-model to deal with select in angular2 </p>
  
  <p>this my html code:</p>
  
  <pre><code>&lt;td *ngIf="classificationCheck"&gt;&lt;select name="classification_type" [(ngModel)]="message.classification_type" 
                      class="form-control" [disabled]="isReply||isForward"&gt;
                              &lt;option value="" disabled default&gt;تصنيف موضوعي&lt;/option&gt;
                              &lt;option *ngFor= "let subType of classificationTypes"&gt;{{subType}}&lt;/option&gt;
                      &lt;/select&gt;&lt;/td&gt;
  </code></pre>
  
  <p>and this onChange function for select1 witch update select2 options:</p>
  
  <pre><code>classificationChange( event ){
  
      if("غير محدد"==event){
          this.classificationCheck=false;
          this.message.classification_type=null;
      }
      else{
          for(let classtype of this.classifications){
  
              if(classtype.gen==event){
                  if(classtype.name)
                      {
                          this.classificationTypes=[];
                          this.classificationCheck=true;
  
                          for(let subType of classtype.name){
                              this.classificationTypes.push(subType);
                          }
                      }
              }
  
          }
      }
  
  }
  </code></pre>