How to Export user input from one JS file to another JS file running on server side

How can I export user input from JS file which running on browser side to the JS file which will be running 开发者_Python百科on server side?

I tried using module. Export but getting error and I also tried to write client side and server-side code in same JS file but again error. If I am using any npm package in client JS file, then gives error. So how should I export value to server-side JS file.