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JavaScript AngularJS An Introduction to Directives Directives: $observe

Ronnie Barua
Ronnie Barua
17,665 Points
Posted by Ronnie Barua
Ronnie Barua
17,665 Points

Can't solve this

Write the code to call console.log with the value of the course-title attribute every time it changes.

app.js 
angular.module('myApp', [])
  .controller('myController', function ($scope) {
    $scope.title = 'My embedded title';
  })
  .directive('treehouseCourse', function () {
    return {
      link: function ($scope, $element, $attrs) {

        $attrs.$observe(courseTitle);

          console.log(courseTitle);

        // YOUR CODE HERE
        }

    }
  });
index.html 
<!DOCTYPE html>
<html ng-app="myApp">
<head>
  <title>Angular.js</title>
  <script src="js/angular.js"></script>
  <script src="app.js"></script>
</head>
<body ng-controller="myController">

  <div treehouse-course course-title="{{title}}"></div>

</body>
</html>

2 Answers

Juan Ferreira
Juan Ferreira
47,991 Points

$observe takes in two parameters - key as a string and a function. The key would refer to the attribute you're monitoring or observing for changes. Where function is a callback every time a change is made. The new value of the attribute is passed in as a parameter to the function parameter.

The result should look like the following:

angular.module('myApp', [])
  .controller('myController', function ($scope) {
    $scope.title = 'My embedded title';
  })
  .directive('treehouseCourse', function () {
    return {
      link: function ($scope, $element, $attrs) {

        $attrs.$observe('courseTitle', function(value){
          console.log(value);
        });

      }
    }
  });
Ronnie Barua
Ronnie Barua
17,665 Points
Ronnie Barua
Ronnie Barua
17,665 Points

Thank you so much Juan for explaining because I'm just a bit confuse here as I progress.