如何将默认值设置为 null 或 0 到 Select 下拉 Angular 7

Question

I have a select drop down code is like this in some cases it is hidden, when the select drop down is hidden i want to send null or 0 instead of empty value when i save the form how to do that.

         <div class="col-md-4" [hidden]="!cpSettlement">
            <select
            class="form-control"
            name="settlement"
            [(ngModel)]="settlement"
            [required]="cpSettlement && payTermOptions"
          >

            <option [value]="'Net'">Net</option>
            <option [value]="'Monthly'">Monthly</option>
            <option [value]="'Quarterly'">Quarterly</option>
          </select>
        </div>

Answer 1

In your save method you can simply do

save() {
   this.settlement = this.cpSettlement ? this.settlement : null;
}

In this case if cpSettlement is true , you'll have the value of settlement from dropdown options. Else if cpSettlement is false means the dropdown is hidden so the value will be null .

UPDATES

            <div class="col-md-4" [hidden]="!cpSettlement">
                <select
                class="form-control"
                name="settlement"
                [(ngModel)]="settlement"
                [required]="cpSettlement && payTermOptions"
              >

                <option value="Net">Net</option>
                <option value="Monthly">Monthly</option>
                <option value="Quarterly">Quarterly</option>
              </select>
            </div>

If you're assigning a static value for the options, you don't need to use angle braces like you did [value] . Instead you should just use as in normal html options values. value="Monthly" .