title: Detect if data in an Angular form (not reactive) was changed
body: <p>I have Angular form (not reactive), with data binded in ngModel:</p>
  
  <pre><code> &lt;form #form="ngForm"&gt;
    &lt;input [(ngModel)]="user.name"&gt;
    &lt;input [(ngModel)]="user.color"&gt;
  
    &lt;button type="submit"&gt;Save&lt;/button&gt;
   &lt;/form&gt;
  </code></pre>
  
  <p>How can i disable submit button if binded data has not been changed?</p>