Javascript Variable Is An Array Of Objects But Can't Access The Elements

I am using Firebase database and Javascript, and I have code that will get each question in each category. I have an object called category will contain the name, the questions, an

Solution 1:

The callback(questionsPerCategory); should happen when all async calls are finished.

Right now the questionsPerCategory is not ready when the callback is called. I would use Promise API to accomplish this.

Depending on the Promise library you are using, this can be accomplished in a different ways, e.g. by using bluebird it looks like you need map functionality.

Solution 2:

Try this code:

this.getQuestionsForEachCategory = function(callback, questions) {
var ref = firebase.database().ref('category');
var questionRef = firebase.database().ref('question');
console.log('get questions for each category');
var questionsPerCategory = [];
// CODE A
ref.once("value", function(snapshot) {

    // CODE B
    snapshot.forEach(function(childSnapshot) {
        var key = childSnapshot.key;

        var childData = childSnapshot.val();

        var category = {
            category_name: childData.category_name
        };

        // CODE C               
        questionRef.orderByChild("category_name").equalTo(childData.category_name).once("value", function(questionSnapshot){
            var count = 0;
            var q = [];

            // CODE D
            questionSnapshot.forEach(function(childQuestionSnapshot) {
                var questionObj = childQuestionSnapshot.val();
                count++;

                questions.push(questionObj.question);
                q.push(questionObj.question);
            });

            category.questions = q;
            category.questionCount = count;
            questionsPerCategory.push(category);

        });
    callback(questionsPerCategory); 
    });
});
};