The Dependent item test works fine,but the data is not actually obtained

Steps to reproduce:

1. Configure a major item，its value is "Huawei Versatile Routing Platform Software
   VRP (R) software, Version 5.160 (ATN V200R005C10SPC100)
   Copyright (C) 2014-2015 Huawei Technologies Co., Ltd.
   ATN950B"
2. Configure an item of a dependency type，Use javascript to preprocess the value of the main item.  
3. After the main item gets the value, the value of the dependency is empty

Result:
See screenshot...

Expected:
I expect the dependent item to correctly return the last line of the main item character "ATN950B"