Give placeholder to select in Angular 6

Question

I have a select option in which i want to give placeholder which says \"select a category\"

Answer 1

simply use [value]="undefined"

<select class="form-control" [(ngModel)]="selectedCategory">
    <option [value]="undefined" disabled hidden>Select...</option>
    <option *ngFor="let c of categories">{{c}}</option>
</select>