protected override void ProcessItem(JsValue[] args, JsValue currentValue) { _index++; var sourceValue = ExtractValueFromIteratorInstance(currentValue); JsValue jsValue; if (!ReferenceEquals(_callable, null)) { args[0] = sourceValue; args[1] = _index; jsValue = _callable.Call(_thisArg, args); } else { jsValue = sourceValue; } _instance.Set((uint)_index, jsValue, updateLength: false, throwOnError: true); }