This does work, you just can’t always copy and paste code from here and expect it to work for you every time, sometimes you have to change it to suit your own site and setup.
It all works for me here, with the Wix tutorial using onClick here.
https://givemeawhisky.wixsite.com/onchangetest
Along with the onChange test here which uses Shan’s code above as a starting point to work off of.
https://givemeawhisky.wixsite.com/onchangetest/test