form.html

<h2>My form</h2>

<form [formGroup]="myForm" (ngSubmit)="onSubmit()">
  <div>
    Make email mandatory <input formControlName="myCheckbox"
                                type="checkbox">
  </div>
  <div>
    Email: <input formControlName="myEmailField"
                  type="email">
  </div>
  <button [formAction]="submit">Submit</button>
</form>

<h2>Debug</h2>
<ul>
  <li>Is my form  valid? {{myForm.valid}}</li>
  <li><pre>{{myForm.controls.myEmailField.errors| json}}</pre></li>
</ul>