How do I iterate through objects stored in a firebase array in JavaScript?

Question

At the moment I am storing a few objects in Firebase. After successfully retrieving the items from Firebase and storing them in a firebaseArray, I want to further thin out the unwanted elements by deleting the elements in the firebaseArray that do not have the desired property. Consider my code at the moment, that does not do as wanted, however there are no errors in the console:

var querylatestPosts = firebase.database().ref("Topics");
$scope.latestPosts = $firebaseArray(querylatestPosts);
console.log($scope.latestPosts) ;
$scope.latestPosts.forEach(function(el) {
 if ($scope.checkWorldview(el) == false) {
   delete $scope.latestPosts.el ;
 }
});

(Note I am unable to log 'el' in the console, nor does the forEach seem to execute, as I can log nothing in the function in the console)

The 'checkWorldview' function behaves as expected when elements are fed in different instances and returns false if the required property is not present in the element under consideration. Thus if the function returns false, I want to delete the specific element in $scope.latestPosts that does not contain the wanted property.

I hope this is clear, thank you in advance for any help you can offer!

cathryngriffiths · Accepted Answer · 2018-06-25 21:27:55Z

2

The way you are using the $firebaseArray isn't recommended by the docs (see here), which state that $firebaseArray is read only and should not be manipulated.

So you have a few options:

Instead of filtering the array on the client-side, you should modify the query you're using to retrieve data from Firebase to only get elements that have the desired property (ex: use 'equalTo' in the query)

OR

Don't use a $firebaseArray because you're not using it in the way it was intended. Use a regular, good ol' fashion JavaScript array instead.

** Also, just a general comment: don't delete elements from an array as you loop through it as this is generally bad practice (we don't expect arrays to have elements added/removed while we loop through them). Instead, use Array.filter.

answered Jun 25, 2018 at 21:27

cathryngriffiths

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1 Comment

Arne Verster Over a year ago

Thanks! I’ll give this a shot.

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