JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://code.angularjs.org/angular-1.0.1.js"></script>
<div ng-controller="Ctrl">
    <h1>Testing directive</h1>
    <input type="text" ng-model="x">
   <span ng-hey="x > 3"></span>
</div>

JavaScript

var myApp = angular.module('myApp',[]);

myApp.controller('Ctrl', ['$scope', '$timeout', function ($scope, $timeout) {
    $timeout(function () {
      $scope.x = 5;
    }, 2000);
  }]);
myApp.directive('ngHey', function () {
    return {
      'restrict': 'A',
       'scope': true,
      'link': function($scope, el, attr) {

        var go = function () {
            if ($scope.$eval(attr.ngHey)) {
              alert('oiiiiiii');
            }
          };

        $scope.$watch('x', function (val) {
          if (val) {
            go();
          }
        });
      }
    };
  });