[Angular HTML] Overwrite input value, String.fromCharCode & input.selectionStart

  @HostListener('keydown', ['$event', '$event.keyCode'])
  onKeyDown($event: KeyboardEvent, keyCode) {
 
    if(keyCode !== TAB) {
      $event.preventDefault();
    }
 
    // get value for the key
    const val = String.fromCharCode(keyCode);
    // get position
    const cursorPos = this.input.selectionStart;
 
    overWriteCharAtPosition(this.input, val, cursorPos);
  }
 
export const overWriteCharAtPosition = (
  input: HTMLInputElement,
  val: any,
  position: number
) => {
  const currentValue = input.value;
  input.value = currentValue.slice(, position) + val + currentValue.slice(position+);
};