Refreshing child table index

Frappe Framework Custom Script
1

How can I just refresh index in a child table?
Tried:

$.each (condition, function(i, d){
   frm.doc.child_table[i].refresh()
});
2

not getting your query but if you want to iterate on child

    $.each (condition, function(i, d){
//here i is index and d is row object of child table
    });