title: Angular 4 Conditional styling
body: <p>I have this html code which works great: </p>
  
  <pre><code>&lt;button class="button-style standard-button button-blue" (click)="onOkClick()"
  [ngClass]="{'disabled': !hasUnsavedNotes()}" [disabled]="!hasUnsavedNotes()"&gt;
  Save and close
  &lt;/button&gt;
  </code></pre>
  
  <p>My question is how do I change class="button-style standard-button button-blue" to class="button-style standard-button button-grey" when hasUnsavedNotes() returns false? Or simply how do I change the button back color when its disabled? Thanks.</p>