Issue with firebase loops

I have this code:

    setProductsToUser: function(productsArr, userId) {
      console.log('***********************************************');

      channelsToActivate = {}
      count = 0

for (var i = 0; i < productsArr.length; i++) {
         console.log('ref.child(user_products).child('+userId+').child('+productsArr[i]+').set(true);')
         count++
         ref.child('products').child(productsArr[i]).once('value', function(productSnap) {
            count--
            console.log(count)
            if(productSnap.val()){
               for (key in productSnap.val().channels) {
                  channelsToActivate[key] = true
                  console.log(channelsToActivate)
               }
               if (count == 0){
                for (key in channelsToActivate) {
                console.log('ref.child(system_user).child('+key+').child('+userId+').set(true);')                  
                console.log('ref.child(user_system).child('+userId+').child('+key+').set(true);')

             }
          }
       } 
    })

}

And I sent code like this:

productsM.setProductsToUser(['com-dummy-dummy-1month'], '2HWdYcvGydTYdrxn2ZGCFsGYV8J2')

productsM.setProductsToUser(['com-dummy-dummy-3months'], '2Wv6tZWC4EO0cb2JivqXLu53S4q1')

The output is:

   ***********************************************
    ref.child(user_products).child(2HWdYcvGydTYdrxn2ZGCFsGYV8J2).child(com-dummy-dummy-1month).set(true);
    ***********************************************
    ref.child(user_products).child(2Wv6tZWC4EO0cb2JivqXLu53S4q1).child(com-dummy-dummy-3months).set(true);
    0
    { '-KUrkIm_pxcACN_ONuWd': true }
    -KUrkIm_pxcACN_ONuWd
    ref.child(system_user).child(-KUrkIm_pxcACN_ONuWd).child(2HWdYcvGydTYdrxn2ZGCFsGYV8J2).set(true);
    ref.child(user_system).child(2HWdYcvGydTYdrxn2ZGCFsGYV8J2).child(-KUrkIm_pxcACN_ONuWd).set(true);
    -1
    { '-KUrkIm_pxcACN_ONuWd': true }

It should be:

***********************************************
ref.child(user_products).child(2HWdYcvGydTYdrxn2ZGCFsGYV8J2).child(com-dummy-dummy-1month).set(true);
0
{ '-KUrkIm_pxcACN_ONuWd': true }
-KUrkIm_pxcACN_ONuWd
ref.child(system_user).child(-KUrkIm_pxcACN_ONuWd).child(2HWdYcvGydTYdrxn2ZGCFsGYV8J2).set(true);
ref.child(user_system).child(2HWdYcvGydTYdrxn2ZGCFsGYV8J2).child(-KUrkIm_pxcACN_ONuWd).set(true);
***********************************************
ref.child(user_products).child(2Wv6tZWC4EO0cb2JivqXLu53S4q1).child(com-dummy-dummy-3months).set(true);
0
{ '-KUrkIm_pxcACN_ONuWd': true }
-KUrkIm_pxcACN_ONuWd
ref.child(system_user).child(-KUrkIm_pxcACN_ONuWd).child(2Wv6tZWC4EO0cb2JivqXLu53S4q1).set(true);
ref.child(user_system).child(2Wv6tZWC4EO0cb2JivqXLu53S4q1).child(-KUrkIm_pxcACN_ONuWd).set(true);

I get succesfully the last output placing a setTimeout with 4 seconds something like this:

productsM.setProductsToUser(['com-dummy-dummy-1month'], '2HWdYcvGydTYdrxn2ZGCFsGYV8J2')

setTimeout(function() {
productsM.setProductsToUser(['com-dummy-dummy-3months'], '2Wv6tZWC4EO0cb2JivqXLu53S4q1')
}, 4000);

How can I reach the desired output without a timeout in every call? (I will loop like one hundred times for that function in my code - setProductsToUser) Why the counter goes to -n ?

via arnoldssss