How should I package plugin functions for use in a validation directive?

Question

I am working on the below validation directive, suggested to me in this answer:

MyBigAngularApp.directive("bkNgValidation", function ($compile) {
    return {
        priority: 10000,
        terminal: true,
        link: function (scope, element, attrs) {

            var validationType = attrs.bkNgValidation;
            window["addValidationFor_" + validationType](element);

            // prevent infinite loop
            element.removeAttr("bk-ng-validation");
            $compile(element)(scope);
        }
    };
});

Then, when I apply this directive to an html element, in the form, bk-ng-validation="phoneNumber", my directive invokes this function:

function addValidationFor_phoneNumber(element) {
    element.attr("ng-pattern", "/^[0-9]+$/");
    element.attr("ng-minlength", 5);
    element.attr("ng-maxlength", 8);
    alert("yeah baby");
}

This addValidationFor_phoneNumber is currently in the global namespace, just for my proof of concept, but I am looking to maybe use a revealing module to organize what could become quite a number of validation functions. Or is there some other pattern I should follow because I am working inside Angular? I suspect I could do something like declare a constant for the revealing module and inject it into the directive, but I thought I'd ask this question before going too far down the wrong road.

Answer 1

Indeed it is generally not recommended to use variables from the global scope in Javascript, and an absolute anti-pattern when working with AngularJS.

What you are looking for is a service (or factory, which does the same job in a slightly different syntax), which would be injected to your directive.

MyBigAngularApp.service('bkService', function() {
  this.phoneNumber   = function(element) { ... }
  this.somethingElse = function(element) { ... }
});

And your directive becomes:

// Note how bkService is injected to the directive in this first line
MyBigAngularApp.directive("bkNgValidation", function ($compile, bkService) {
  return {
    priority: 10000,
    terminal: true,
    link: function (scope, element, attrs) {

        var validationType = attrs.bkNgValidation;
        bkService[validationType](element);

        // prevent infinite loop
        element.removeAttr("bk-ng-validation");
        $compile(element)(scope);
    }
  };
});

---

Now if the only directive that will use this service is that one, you don't really need to create a service but can simply wrap all these functions as private methods from bkNgValidation:

MyBigAngularApp.directive("bkNgValidation", function ($compile) {

  var validations = {
    phoneNumber:   function(element) { ... }
    somethingElse: function(element) { ... }
  };

  return {
    priority: 10000,
    terminal: true,
    link: function (scope, element, attrs) {

        var validationType = attrs.bkNgValidation;
        validations[validationType](element);

        // prevent infinite loop
        element.removeAttr("bk-ng-validation");
        $compile(element)(scope);
    }
  };
});