ng-validation-border#host-binding.ts

@HostBinding('style.border-style')
get borderStyleCss() {
  return this.showBorder ? this.borderStyle : null;
}

@HostBinding('style.border-width')
get borderWidthCss() {
  return this.showBorder ? this.borderWidth : null;
}

@HostBinding('style.border-color')
get borderColorCss() {
  return this.showBorder ? this.colors[this.ngControl.status] : null;
}

get showBorder() {
  return this.ngControl.dirty || this.ngControl.touched;
}