163     JSMutableHandle<JSTaggedValue> element(thread, JSTaggedValue::Undefined());  in FlattenIntoArray()  local
171     //         i. Let element be ? Get(source, P).  in FlattenIntoArray()
173 …//             1. Set element to ? Call(mapperFunction, thisArg, « element, sourceIndex, source »).  in FlattenIntoArray()
176     //             1. Set shouldFlatten to ? IsArray(element).  in FlattenIntoArray()
180     //             3. Let elementLen be ? LengthOfArrayLike(element).  in FlattenIntoArray()
181 …//             4. Set targetIndex to ? FlattenIntoArray(target, element, elementLen, targetIndex, …  in FlattenIntoArray()
184 …//             2. Perform ? CreateDataPropertyOrThrow(target, ! ToString(!(targetIndex)), element).  in FlattenIntoArray()
194             element.Update(JSArray::FastGetPropertyByValue(thread, thisObjVal, p).GetTaggedValue());  in FlattenIntoArray()
197                 const int32_t argsLength = 3; // 3: « element, sourceIndex, source »  in FlattenIntoArray()
202 …       info->SetCallArg(element.GetTaggedValue(), p.GetTaggedValue(), thisObjVal.GetTaggedValue());  in FlattenIntoArray()
205                 element.Update(obj);  in FlattenIntoArray()
209                 shouldFlatten = element->IsArray(thread);  in FlattenIntoArray()
214                 tempArgs.sourceLen = ArrayHelper::GetLength(thread, element);  in FlattenIntoArray()
216 …         JSTaggedValue TargetIndexObj = FlattenIntoArray(thread, newArrayHandle, element, tempArgs,  in FlattenIntoArray()
231 …           JSObject::CreateDataPropertyOrThrow(thread, newArrayHandle, targetIndexHandle, element);  in FlattenIntoArray()