How to Limit the Number of fields added in Multifield and give pop-up alert in AEM 6.4 Touch UI

Hi all,

I having the issue with limiting the number of fields in touch ui

In my scenario the multifield values are storing as JSON array and maximum number of fields added in the multifield is 6. If they try to add more than six field mean that time i want to give a pop-up alert message that shown like Maximum six field should be added.

I tried custom js but that is working well when the multifield values are stored by node by node like item0,item1,item2,etc.but in my case values storing as JSON Array

Kindly give me some solution to resolve this issue.