Return Sum of Specific Type

In the example code below the cost_field captures the cost while the item_type_field is used to capture the type of item that the cost is associated with in a child record. The code then loops through comparing the two arrays and returns a sum of all values in the cost_field where the item_type_field is equal to Item A.

  var cost = REPEATABLEVALUES($repeatable_section, 'cost_field');
  var items = REPEATABLEVALUES($repeatable_section, 'item_type_field').map(CHOICEVALUE);

  var total = 0;

  for (var i = 0; i < cost.length; ++i) {
    if (items[i] === 'Item A') {
      total += NUM(cost[i]);
    }
  }

  SETRESULT(total)
}