<select class="form-control" [value]="defaultSelectedCurrency" formControlName="currency">
<option *ngFor="let item of currency" [value]="item.value" [selected]="item.isSelected">{{item.key}}</option>
</select>
currency = [
{ key: 'USD', value: 'USD', isSelected: true },
{ key: 'AUD', value: 'AUD', isSelected: false }
];
defaultSelectedCurrency: string;
ngOnInit() {
this.defaultSelectedCurrency = this.currency[0].value;
}