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JavaScript AngularJS An Introduction to Two-Way Data Binding Two-Way Binding: watchers

Posted by Thomas Conroy
Thomas Conroy
193 Points

Why do we pass in the desired object property to watch as a string, instead of the literal notation?

I was just wondering why we do this in angular -- why pass it as a string, instead of explicitly passing the property?

i.e, we do this:

  $scope.$watch('user.id', function(newVal, oldVal){
    //...
  });

instead of:

  $scope.$watch(user.id, function(newVal, oldVal){
    //...
  });
app.js 
angular.module('myApp', [])
.controller('myController', function ($scope, $http) {
  $scope.user = {name: 'Alex', id: 123};

  getUserData = function (id) {
    console.log('Getting user with ID: ' + id);
  }

  // YOUR CODE HERE
  $scope.$watch('user.id', function(newVal, oldVal){
    getUserData(newVal);
  });

});
index.html 
<!DOCTYPE html>
<html ng-app="myApp">
<head>
  <title>Angular.js</title>
  <script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.3.2/angular.min.js"></script>
  <script src="app.js"></script>
</head>
<body ng-controller="myController">

  <input type="text" ng-model="user.id" />

</body>
</html>