EncodeApp is a GAS library for retrieving the encoding set (charset) and doing URL encode with the specific encoding set using Google Apps Script (GAS).
You can see the detail information here https://github.com/tanaikech/EncodeApp
This is a sample script for achieving the URL encode with Shift-JIS using Google Apps Script.
Unfortunately, there are no methods for directly achieving above in the methods of Google Apps Script. So it is required to prepare it as the script. In order to use Shift-JIS of the character set at Google Apps Script, it is required to use it as the binary data. Because, when the value of Shift-JIS is retrieved as the string by Google Apps Script, the character set is automatically changed to UTF-8. Please be careful this.