Repository: angular/angular.js
File: src/ng/directive/ngModel.js (JavaScript)

Code before:
        idx = formatters.length;

    var viewValue = this.$modelValue;
    while (idx--) {
      viewValue = formatters[idx](viewValue);
    }

    return viewValue;
  },

  /**
   * This method is called internally when the bound scope value changes.
   */
  $$setModelValue: function(modelValue) {
    this.$modelValue = this.$$rawModelValue = modelValue;
    this.$$parserValid = undefined;
    this.$processModelValue();
  },

  $$setUpdateOnEvents: function() {
    if (this.$$updateEvents.length > 0) {
      this.$$element.off(this.$$updateEvents, this.$$updateEventHandler);
    }

    this.$$updateEvents = this.$options.getOption('updateOn');
    this.$$element.on(this.$$updateEvents, this.$$updateEventHandler);
  },

  $$updateEventHandler: function(ev) {
    this.$$debounceViewValueCommit(ev && ev.type);
  }
};

function setupModelWatcher(ctrl) {
  // model -> value
  // Note: we cannot use a normal scope.$watch as we want to detect the following:
  // 1. scope value is 'a'
  // 2. user enters 'b'
  // 3. ng-change kicks in and reverts scope value to 'a'
  //    -> scope value did not change since the last digest as
  //       ng-change executes in apply phase
  // 4. view should be changed back to 'a'
  ctrl.$$scope.$watch(function ngModelWatch(scope) {
    var modelValue = ctrl.$$ngModelGet(scope);

    // if scope model value and ngModel value are out of sync
    // This cannot be moved to the action function, because it would not catch the
    // case where the model is changed in the ngChange function or the model setter
    if (modelValue !== ctrl.$modelValue &&
      // checks for NaN is needed to allow setting the model to NaN when there's an asyncValidator
      // eslint-disable-next-line no-self-compare

Review comment (suggestion):
I think it would be better to avoid this call if `$$updateEvents` are empty. (Several operations take place unnecessarily.)

Code after:
        idx = formatters.length;

    var viewValue = this.$modelValue;
    while (idx--) {
      viewValue = formatters[idx](viewValue);
    }

    return viewValue;
  },

  /**
   * This method is called internally when the bound scope value changes.
   */
  $$setModelValue: function(modelValue) {
    this.$modelValue = this.$$rawModelValue = modelValue;
    this.$$parserValid = undefined;
    this.$processModelValue();
  },

  $$setUpdateOnEvents: function() {
    if (this.$$updateEvents) {
      this.$$element.off(this.$$updateEvents, this.$$updateEventHandler);
    }

    this.$$updateEvents = this.$options.getOption('updateOn');
    if (this.$$updateEvents) {
      this.$$element.on(this.$$updateEvents, this.$$updateEventHandler);
    }
  },

  $$updateEventHandler: function(ev) {
    this.$$debounceViewValueCommit(ev && ev.type);
  }
};

function setupModelWatcher(ctrl) {
  // model -> value
  // Note: we cannot use a normal scope.$watch as we want to detect the following:
  // 1. scope value is 'a'
  // 2. user enters 'b'
  // 3. ng-change kicks in and reverts scope value to 'a'
  //    -> scope value did not change since the last digest as
  //       ng-change executes in apply phase
  // 4. view should be changed back to 'a'
  ctrl.$$scope.$watch(function ngModelWatch(scope) {
    var modelValue = ctrl.$$ngModelGet(scope);

    // if scope model value and ngModel value are out of sync
    // This cannot be moved to the action function, because it would not catch the
    // case where the model is changed in the ngChange function or the model setter
    if (modelValue !== ctrl.$modelValue &&