title: How to create a select box using ngFor with only unique results
body: <p>I'm trying to create a search filter to filter results by a certain category. So for instance, take an array of employees, I want to create a select box with each employees department selectable.</p>
  
  <p>I've tried to find tutorials and such on this but despite being what I assume is not an uncommon question, I cannot seem to find any. Below is my current code, though very standard.</p>
  
  <pre><code>&lt;select&gt;
     &lt;option *ngFor="let employee of employees"&gt;
        {{employee.Department}}
     &lt;/option&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p>if i use ngFor in the standard way, I get a select box that renders with the following options:</p>
  
  <p>HR
  HR
  HR
  Management
  Programming
  Programming</p>
  
  <p>How do I operate my ngFor in such a way where options that exist already are not added, which is to say, change the select box to have only these options:</p>
  
  <p>HR
  Management
  Programming</p>