document.getElementById('loginInput').value = '123';

<input type='text' id='loginInput' #abc/>

this.abc.nativeElement.value

ngAfterViewInit(){
    document.getElementById('loginInput').value = '123344565';
  }

(<HTMLInputElement>document.getElementById('loginInput')).value = '123';

<input type="text" [(ngModel)]="username" [ngModelOptions]='{standalone: true}'/>
<input type="text" [(ngModel)]="password" [ngModelOptions]='{standalone: true}'/>

username: 'whatever'
password: 'whatever'