$scope.$watch on some part of object in array

Question

There is an array as below, which stores a mixture of data and styles in it.

User is able to add, remove or re-order its elements, as well as modify value of elements, so I need to watch it with $scope.$watch to do something if it's modified.

However, I don't want to get notified if only its style changes. Is there any better practice to arrange my data, to get notified only if value is changed, thank you.

Plunker

[{
  value: 1,
  selected: true,
  width: '100px'
}, {
  value: 2,
  width: '150px'
}, {
  value: 3,
  width: '100px'
}];

Just to confirm a few things: (1) the only property you want to be notified of changing is value? (2) should the watcher also ignore any shuffling of the order of the data? (3) watcher definitely preferable to ng-change, etc? — JcT
– JcT, Commented Jun 23, 2015 at 12:43
@JcT (1) There may be a few values I need to get notified (2) The order of array shouldn't be ignored (3) It may not be from <input>, so I don't think ng-change is applicable. Thanks.. — Haocheng
– Haocheng, Commented Jun 24, 2015 at 1:07

Bharat · Accepted Answer · 2015-06-23 11:44:12Z

1

This is an example to watch only when style changes.

http://plnkr.co/edit/GAG40qBkD4eq3GbKBMhc?p=preview

$scope.$watch(function($scope) {
    return $scope.data.
    map(function(data) {
        return data.width;
    });
}, function(newValue) {
    console.log('Modified width' + newValue);
}, true);

I think similarly you will have to create watch on needed attributes.

Source: http://blogs.microsoft.co.il/choroshin/2014/03/26/angularjs-watch-for-changes-in-specific-object-property/

answered Jun 23, 2015 at 11:44

Bharat

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Comments

dieuvn3b · Accepted Answer · 2015-06-23 08:59:39Z

0

Call $watch with true as the third argument:

 $scope.$watch('data', function(newValue, oldValue) {
    console.log(newValue, oldValue);
  },true);

answered Jun 23, 2015 at 8:59

dieuvn3b

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3 Comments

Haocheng Over a year ago

Thanks, but in this case, changing of style will also invoke watcher.

dieuvn3b Over a year ago

when change of style, compare newValue[1].width and oldValue[1].width. If not equal,not do anything

Haocheng Over a year ago

hmm but that can't guarantee that others didn't change.

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