angularjs: custom directive to check if a username exists

Question

I have my registration form with textbox username. I want to do is when the user enter the username, the custom directive will check if the entered username is exists in the

Answer 1

there is a great tutorial by yearofmoo about $asyncvalidators in angular1.3. it allows you to easily show pending status when the field is being checked by the backend:

here's a working plnkr

app.directive('usernameAvailable', function($timeout, $q) {
  return {
    restrict: 'AE',
    require: 'ngModel',
    link: function(scope, elm, attr, model) { 
      model.$asyncValidators.usernameExists = function() {

        //here you should access the backend, to check if username exists
        //and return a promise
        //here we're using $q and $timeout to mimic a backend call 
        //that will resolve after 1 sec

        var defer = $q.defer();
        $timeout(function(){
          model.$setValidity('usernameExists', false); 
          defer.resolve;
        }, 1000);
        return defer.promise;
      };
    }
  } 
});

html:

<form name="myForm">
  <input type="text" 
        name="username"
        ng-model="username" 
        username-available 
        required
        ng-model-options="{ updateOn: 'blur' }">
  <div ng-if="myForm.$pending.usernameExists">checking....</div>
  <div ng-if="myForm.$error.usernameExists">username exists already</div>
</form>

note the use of ng-model-options, another cool feature of 1.3

---

edit

here's a plnkr that shows how to use $http in the directive. note that it is only requesting another .json file, that contains a true/false value. and the directive will set validity on the ng-model accordingly.