Ion-list / ion-item and parallel queries/promises

Hi, is there any way to run background queries in order to calculate some values, example: rating count, and display each item asynchronously ?

You know, my list is already populated. And I have to wait for queries triggered for each item, however, I’d like to know how to populate the results of those queries for its respectively item.

Is there any way?

To run on background:

setTimeout( yourFunction, 0 );

function yourFunction(){
//Calculate
}