Monitoring a specific property within an array of objects with AngularJS

Question

Monitoring a specific property within an array of objects with AngularJS

I am facing an issue with the data in my controller

    $scope.data = {
        home: {
            baseValue: "1",
            name: "home"
        },
        contact: {
            baseValue: "2",
            name: "contract"
        }
     // numerous other options
    };

How can I simplify the process of determining when the baseValue changes without having to loop through all the arrays?

Here is a snippet of my HTML:

<section class="content row" ng-repeat="item in data">
   {{item.name}}
   ....
</section>

I have tried using a general $watch function, but it requires me to iterate through each object individually.

$scope.$watch('data', function (newValue, oldValue, scope) {
 // code for comparing the arrays line by line
}, true);

Any suggestions on how to implement a more efficient $watch to only track changes in the baseValue property?

For related queries, check out these links:

AngularJS watch array of objects for data change
How to get an object that was changed in angularjs?
How to deep watch an array in angularjs?

UPDATE 1

If there are multiple objects in the data set, adding individual $watch functions for each object could become messy and inefficient. Any suggestions on improving this process?

$scope.$watch('data.home', function (newValue, oldValue, scope) {
 // logic for handling newvalue.baseValue
}, true);

$scope.$watch('data.contact', function (newValue, oldValue, scope) {
 // logic for handling newvalue.baseValue
}, true);
... // Add more individual `watch` functions

javascript angularjs

Answer 1

Answer №1

After analyzing your query, I suggest utilizing ngChange to monitor changes in the baseValue and then trigger the function accordingly.

Here is an example of how you can implement this:

<section class="content row" ng-repeat="item in data">
    Name: {{item.name}} <br/>
    BaseValue: <input type="text" ng-model="item.baseValue" ng-change="baseValueChange(item.baseValue)"/>
</section>

To handle a more advanced scenario where you need both the oldValue and newValue, you can check out this plunkr - http://plnkr.co/edit/hqWRG13gzT9H5hxmOIkO?p=preview

Here's how you would modify the HTML for that:

<section class="content row" ng-repeat="item in data">
    Name: {{item.name}} <br/>
    BaseValue: <input type="text" ng-init="item.oldBaseValue = item.baseValue" ng-model="item.baseValue" ng-change="baseValueChange(item.oldBaseValue, item.baseValue); item.oldBaseValue = item.baseValue"/>
</section>

And the corresponding Controller code:

$scope.baseValueChange = function(oldVal, newVal) {
    console.log("base value change", oldVal, newVal);
}

Answer 2

After analyzing your query, I suggest utilizing ngChange to monitor changes in the baseValue and then trigger the function accordingly.

Here is an example of how you can implement this:

<section class="content row" ng-repeat="item in data">
    Name: {{item.name}} <br/>
    BaseValue: <input type="text" ng-model="item.baseValue" ng-change="baseValueChange(item.baseValue)"/>
</section>

To handle a more advanced scenario where you need both the oldValue and newValue, you can check out this plunkr - http://plnkr.co/edit/hqWRG13gzT9H5hxmOIkO?p=preview

Here's how you would modify the HTML for that:

<section class="content row" ng-repeat="item in data">
    Name: {{item.name}} <br/>
    BaseValue: <input type="text" ng-init="item.oldBaseValue = item.baseValue" ng-model="item.baseValue" ng-change="baseValueChange(item.oldBaseValue, item.baseValue); item.oldBaseValue = item.baseValue"/>
</section>

And the corresponding Controller code:

$scope.baseValueChange = function(oldVal, newVal) {
    console.log("base value change", oldVal, newVal);
}

Answer 3

Answer №2

Observing an object attribute is possible.
An example of this can be seen below:

for(let property in $scope.data) {
  if($scope.data.hasOwnProperty(property)) {
    $scope.$watch("data['" + property + "'].baseValue", function(value, oldValue) {
      // Carry out desired actions
    });
  }
}

This code has not been executed, but the concept is straightforward.

Answer 4

Observing an object attribute is possible.
An example of this can be seen below:

for(let property in $scope.data) {
  if($scope.data.hasOwnProperty(property)) {
    $scope.$watch("data['" + property + "'].baseValue", function(value, oldValue) {
      // Carry out desired actions
    });
  }
}

This code has not been executed, but the concept is straightforward.

Answer 5

Answer №3

In this particular situation, the only way to handle it is by utilizing multiple watches. Another approach is to use $watchCollection to monitor an array of object values. You can retrieve this array by using the Object.values method.

scope.$watchCollection(function() {
    return Object.values(obj);
}, function(newValues, oldValues) {
    // By monitoring all the values, you can track changes!
    // If you want a callback to be triggered with the object as an argument:
    if (angular.isFunction(scope.callback())) {
        scope.callback()(obj);
    }
});

Answer 6

In this particular situation, the only way to handle it is by utilizing multiple watches. Another approach is to use $watchCollection to monitor an array of object values. You can retrieve this array by using the Object.values method.

scope.$watchCollection(function() {
    return Object.values(obj);
}, function(newValues, oldValues) {
    // By monitoring all the values, you can track changes!
    // If you want a callback to be triggered with the object as an argument:
    if (angular.isFunction(scope.callback())) {
        scope.callback()(obj);
    }
});

Answer 7

Answer №4

This is the solution I used to solve the problem:

$scope.updateFields= function(){
    angular.forEach($scope.fields,function (value, key) {
        value.title = value.title.toLowerCase().replace(/\s+/g,'');
    })
};
$scope.$watch('fields', $scope.updateFields, true);

Answer 8

This is the solution I used to solve the problem:

$scope.updateFields= function(){
    angular.forEach($scope.fields,function (value, key) {
        value.title = value.title.toLowerCase().replace(/\s+/g,'');
    })
};
$scope.$watch('fields', $scope.updateFields, true);

Monitoring a specific property within an array of objects with AngularJS

Answer №1

Answer №2

Answer №3

Answer №4

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