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javascript - Get Firebase child nodes' names without getting their children too in Firebase response?

I have the following hierarchy on firebase, some data are hidden for confidentiality:

enter image description here

I'm trying to get a list of videos IDs (underlines in red)

I only can get all nodes, then detect their names and store them in an array!
But this causes low performance; because the dataSnapshot from firebase is very big in my case, so I want to avoid retrieving all the nodes' content then loop over them to get IDs, I need to just retrieve the IDs only, i.e. without their nested elements.

Here's my code:

new Firebase("https://PRIVATE_NAME.firebaseio.com/videos/").once(
    'value', 
    function(dataSnapshot){ 

        // dataSnapshot now contains all the videos ids, lines & links
        // this causes many performance issues

        // Then I need to loop over all elements to extract ids !
        var videoIdIndex = 0;
        var videoIds = new Array();

        dataSnapshot.forEach(
            function(childSnapshot) {
                videoIds[videoIdIndex++] = childSnapshot.name();
            }
        );

    }
);

How may I retrieve only IDs to avoid lot of data transfer and to avoid looping over retrived data to get IDs ? is there a way to just retrive these IDs directly ?

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