form validation

directives.js

angular.module("kp.account")
  /**
   *  @ngdoc        directive
   *  @name         kp.account.directive:kpNicknameValidation
   *  @description
   *  Defines validNickname method.
   *  length between 5-20,less than 5 digit numbers
   */
  .directive("kpNicknameValidation", function() {
    return {
      require: 'ngModel',
      link: function(scope, ele, attr, ctrl) {
        ctrl.$validators.validNickname = function(modelValue, viewValue) {
          //required
          if (!viewValue) {
            return false;
          }
          var length = viewValue.length;
          //length between 5-20
          if (length > 20 || length < 5) {
            return false;
          }
          //less than 5 digit numbers
          var matched = viewValue.match(/[0-9]/g);
          if (matched !== null && matched.length > 5) {
            return false;
          }
          return true;
        }
      }
    }
  });