convert "bad" array in a property of items in a list.

var ref // Firebase ref to your list that has items with bad arrays in them.
var arrayToChange // String of the name of the property that contains the bad array.

ref.once("value", function(snapshot) {
  snapshot.forEach(function(listItem){
    var goodArray = $firebaseArray(listItem.ref().child(arrayToChange));
    listItem.child(arrayToChange).forEach(function(arrayItem){
      var arrayItemVal = arrayItem.val();
      arrayItem.ref().remove();
      goodArray.$add(arrayItemVal);
    });
  });
});