component.html (What you named you form)
<form [formGroup]="contactForm">
(add click event (click)="clearForm())
<button (click)="onSubmit()" (click)="clearForm()" type="submit" class="btn waves-light" mdbWavesEffect>Send<i class="fa fa-paper-plane-o ml-1"></i></button>
component.ts
clearForm() {
this.contactForm.reset();
}
view all code: https://ewebdesigns.com.au/angular-6-contact-form/ How to add a contact form with firebase