Hello World directive

<!DOCTYPE html>
<html>

  <head>
    <script data-require="angular.js@1.4.6" data-semver="1.4.6" src="https://cdnjs.cloudflare.com/ajax/libs/angular.js/1.4.6/angular.min.js"></script>
    <script src="script.js"></script>
  </head>

  <body ng-app="directiveHelloWorld">
    <h1>
      <hello-world></hello-world>
    </h1>
  </body>

</html>

// Code goes here

angular.module('directiveHelloWorld', [])
.directive('helloWorld', function() {
  return {
    restrict: 'E',
    template: '<div>Hello world!</div>'
  };
});