cara menggunakan tersembunyi di div dalam sudut
<div *ngIf="edited" class="alert alert-success box-msg" role="alert">
<strong>List Saved!</strong> Your changes has been saved.
</div>
<div [hidden] = "email.valid || email.pristine" class="alert alert-danger" >
Email is required !!!
</div>
Cheerful Caribou