title: Angular 7 add price, quantity and vat of services dynamically added to form array
body: <p>I have a form array using form builder and each array contains a service. I want to add the price, amount, and vat for each service and display that in the total column. I know that I have to listen to the input changes using valueChange method but I am not sure how to get the index for each service and apply the value to the total column. This code is currently what I have any help would be much appreciated</p>
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>  addValues() {
      var services = this.invoiceForm.get('service');
      services.valueChanges.subscribe(
        val =&gt; {
          console.log(val)
        }
      );
    }</code></pre>
  </div>
  </div>
  </p>
  <p>So far when I edit a field it prints the service form array but how can I get the individual service fields and add them together each time there is a change?</p>