title: Toggle select menu options based on another fields value in FormGroup
body: <p>I am trying to toggle between 2 sets of options given, another select menu's value. I am struggling with a way to do this. I currently have:</p>
  <p>Project Type:</p>
  <pre><code>&lt;div class=&quot;form-group col-md-6&quot;&gt;
          &lt;label&gt;Project Type&lt;/label&gt;
          &lt;select
            class=&quot;form-control&quot;
            formControlName=&quot;projectType&quot;
          &gt;
            &lt;option value=&quot;&quot;&gt;&lt;/option&gt;
            &lt;option
              *ngFor=&quot;let type of ['Team Supplementation', 'Project']&quot;
              [ngValue]=&quot;type&quot;
            &gt;
              {{ type }}
            &lt;/option&gt;
          &lt;/select&gt;
  &lt;/div&gt;
  </code></pre>
  <p>Project Phase:</p>
  <pre><code>&lt;div class=&quot;form-group col-md-6&quot;&gt;
          &lt;label&gt;Project Phase&lt;/label&gt;
          &lt;select
            class=&quot;form-control&quot;
            formControlName=&quot;projectPhase&quot;
            [ngClass]=&quot;{
              'is-invalid':
                projectForm.get('projectPhase').errors &amp;&amp;
                projectForm.get('projectPhase').touched
            }&quot;
          &gt;
            &lt;option value=&quot;&quot;&gt;&lt;/option&gt;
            &lt;option
              *ngFor=&quot;
                let phase of getPhases()
              &quot;
              [ngValue]=&quot;phase&quot;
            &gt;
              {{ phase }}
            &lt;/option&gt;
          &lt;/select&gt;
  &lt;/div&gt;
  </code></pre>
  <p>I need the options of projectPhase to change when the value of projectType is selected. I have two array of strings for each projectType. What should I do to allow this to happen?</p>