select default value in dropdown angular code example

Example 1: in select option how to make one default in angular

<option [ngValue]="undefined" selected>Select</option>

Example 2: set default value in dropdown angular 7

Set validation.min with required as well like below one.

supplierId: ["", [Validators.required, Validators.min(1)]]
supplierId is always greater zero so min(1) works for you.