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

Israel Bautista
Israel Bautista
2,391 Points
Posted by Israel Bautista
Israel Bautista
2,391 Points

so this was my attempt to solve this but didn't worked, not sure why not, the lecture is not very helpful :(

$scope.$watch('user.id', function(newValue, oldValue){ if(newValue){ $scope.user = getUserData(id); } })

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);
  }

  $scope.$watch('user.id', function(newValue, oldValue){
    if(newValue){
      $scope.user = getUserData(id);
    }
  })

});
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>

2 Answers

Salman Akram
PLUS
Salman Akram
Courses Plus Student 40,065 Points
Salman Akram
Salman Akram
Courses Plus Student 40,065 Points

I had similar issue with Two-Way Binding for Watcher, here's explain by Curtis in better example

Colin Bell
Colin Bell
29,679 Points
Colin Bell
Colin Bell
29,679 Points

This question is asking you to watch value of the user.id. If it changes to a new value, take that same new value and run it through the getUserData() function.

In this case, it wants to the check if user.id changes. If it does change (i.e. if it gets a new Value), take that new value and log it to the console preceded by the string "Getting user with ID:"

You don't need to add $scope.user before getUserData. You've already set up your scope with the line

$scope.$watch('user.id',function(newValue, oldValue)

If you run:

  $scope.$watch('user.id',function(newValue, oldValue) {
    if(newValue) {         // If this user.id receives a newValue is true, then
     getUserData(newValue); // Take that same newValue and run it through getUserData
    }
  })

and click on the preview tab and open up the console on your browser, you should see something like this: Console log of getUserData