Angular Form validation: match

gistfile1.js

.directive('match', function() {
    return {
        require: 'ngModel',
        restrict: 'A',
        scope: {
            match: '='
        },
        link: function(scope, elem, attrs, ngModel) {
            scope.$watch(function() {
                return (ngModel.$pristine && angular.isUndefined(ngModel.$modelValue)) || scope.match === ngModel.$modelValue;
            }, function(currentValue) {
                ngModel.$setValidity('match', currentValue);
            });
        }
    };
})