Example of directive with ng-forward

directive.js

import { Directive, Inject } from 'ng-forward';

@Directive({
    selector: '[value-to-check]',
})
@Inject('$scope', '$attrs', 'ngModel')

export default class CheckEqual {
    constructor($scope, $attrs, ngModel) {
        // Add functionality to check the value when the model value changes
        ngModel.$validators.equal = value => $scope.$eval($attrs.valueToCheck) === value;

        $scope.$watch($attrs.valueToCheck, () => {
            ngModel.$validate();
        });
    }
}