ngModel.NgModelController.$formatters

Array of functions to execute, as a pipeline, whenever the model value changes. The functions are called in reverse array order, each passing the value through to the next. The last return value is used as the actual DOM value. Used to format / convert values for display in the control.

function formatter(value) {
  if (value) {
    return value.toUpperCase();
  }
}
ngModel.$formatters.push(formatter);