Passing in the arguments to _handleInput

example-tel-input-example.html

<div [formGroup]="parts" ...>
  <input ... formControlName="area" 
         (input)="_handleInput(parts.controls.area,exchange)" #area>
  ...
  <input ... formControlName="exchange" 
         (input)="_handleInput(parts.controls.exchange,subscriber)" #exchange>
  ...
  <input ... formControlName="subscriber" 
         (input)="_handleInput(parts.controls.subscriber,subscriber)" #subscriber>
</div>