Assign value in javascript

Question

I have two objects : $scope.objectA and $scope.objectB. I assign value from $scope.objectA to $scope.objectB like this:

$scope.objectB.value1 = $scope.objectA.value1;

then I make value1 of $scope.objectB to null;

$scope.objectB.value1 = null;

My question is why when I assign $scope.objectB.value1 to null, $scope.objectA.value1 is null too. How can I keep value of $scope.objectA.value1 while changing value of $scope.objectB.value1?

In your code you only use $scope.objectB

RiesvGeffen
– RiesvGeffen

2016-01-19 07:32:15 +00:00
Commented Jan 19, 2016 at 7:32 — RiesvGeffen
– RiesvGeffen, Commented Jan 19, 2016 at 7:32

Nighisha John · Accepted Answer · 2016-01-19 07:32:26Z

3

Make copy of object B and assign it to the object A. Use angular.copy function. It will creates a deep copy of source.

For more information Visit Angular copy doc

$scope.objectA.value1 = angular.copy($scope.objectB.value1);

answered Jan 19, 2016 at 7:32

Nighisha John

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Comments

Egan Wolf · Accepted Answer · 2016-01-19 07:33:13Z

2

Because this is how it works. You make these two variables "bound" together. If you want to keep value of objectA, then use

$scope.objectB.value1 = angular.copy($scope.objectA.value1);

answered Jan 19, 2016 at 7:33

Egan Wolf

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Ильяс Гарифуллин · Accepted Answer · 2016-01-19 07:43:57Z

1

I think this can happen only if ObjectA and ObjectB refer to the same object on the heap, i.e. it ObjectA and ObjectB are the same objects

$scope['object1'] = {};
$scope['object1']['val'] = {};
$scope['object2'] = {};
$timeout(() => {
  this.$scope['object2']['val'] = this.$scope['object1']['val'];
  $timeout(() => {
   this.$scope['object2']['val'] = null;
      console.log(this.$scope['object1']['val']); // Object {}
    })
});

-

 $scope['object1'] = {};
    $scope['object1']['val'] = {};
    $scope['object2'] = {};
    $timeout(() => {
      this.$scope['object2']['val'] = this.$scope['object1']['val'];
      $timeout(() => {
       this.$scope['object2']['val'] = null;
          console.log(this.$scope['object1']['val']); // null
        })
    });

edited Jan 19, 2016 at 7:43

answered Jan 19, 2016 at 7:38

Ильяс Гарифуллин

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Comments

Muhammad Hamada · Accepted Answer · 2016-01-19 07:50:31Z

1

The reason is when you assign object to a variable, the assignment will be by reference, so the old and new will be a reference to the original object

So when you edit an object, you're actually editing the original object.

The solution

Angular: use object = angular.copy(myObject1)
jQuery: object = $.extend({}, myObject1);

answered Jan 19, 2016 at 7:50

Muhammad Hamada

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