title: Angular 2 ngModelChange old value
body: <p>Can someone please tell me what is the best practice for comparing ngModel old and new value?</p>
  
  <p>In angular 1:</p>
  
  <pre><code>$scope.$watch('someProperty', funciton(oldVal, newVal){
      // code goes here
  })
  </code></pre>
  
  <p>I am asking this because <code>(ngModelChange)</code> never brings me the <code>oldVal</code> , only the <code>newVal</code>.</p>
  
  <p>In my case, I am using ngModel in a <code>&lt;select&gt;</code> tag and compare the old selection with the new one:</p>
  
  <pre><code>&lt;select [(ngModel)]="current" (ngModelChange)="onModelChange($event)"&gt;
       &lt;option *ngFor="let item of myArray" [ngValue]="item"&gt;{{item.name}} &lt;/option&gt;
  &lt;/select&gt;
  </code></pre>