So, a repeater in WIX has to have different IDs for each element inside of it, otherwise it is not going to work. And the method you are trying to use, receives an array of elements IDs that are present on the current repeater data, and a callback function that runs on each element on the repeater that you specified on the array of IDs.
Would you care to explain what are you trying to do so I can assist you in a better way?