title: Change color of selected link in angular 4
body: <p>I made a header using bootstrap 4 but  I want that when I click on any link, link change its color and remains selected.</p>
  
  <pre><code>&lt;nav&gt;
      &lt;div class="collapse navbar-collapse justify-content-end" id="nav-content"&gt;
          &lt;ul class="navbar-nav" id="nav"&gt;
            &lt;li class="nav-item"&gt;
              &lt;a class="nav-link" routerLink=""&gt;About&lt;/a&gt;
            &lt;/li&gt;
            &lt;li class="nav-item"&gt;
              &lt;a class="nav-link" routerLink="/experience"&gt;Experience&lt;/a&gt;
            &lt;/li&gt;
            &lt;li class="nav-item"&gt;
              &lt;a class="nav-link" routerLink="/skills"&gt;Skills&lt;/a&gt;
            &lt;/li&gt;
          &lt;ul&gt;
       &lt;div&gt;
  &lt;nav&gt;
  </code></pre>
  
  <p>I don't know what to do next, I don't want to use jquery.</p>
  
  <p>Please help me.</p>