if you want to set value than you can do the same in some function on click or on some event fire.

also you can get value using ViewChild using local variable like this

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

and get value like this

this.abc.nativeElement.value

here is working example

Update

okay got it , you have to use ngAfterViewInit method of angualr2 for the same like this

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

ngAfterViewInit will not throw any error because it will render after template loading