How to implement form validation?

Question

JavaScript

There is a form on the frontend (Vue).
After submitting, the form is processed on the server (Express), and it sends its content to my mail.
How to implement an output about successful processing on the client?
Front and backend are separate applications on different domains.

Answer 1

What's the problem? Do you exchange via ajax? Return a response after being processed by the server. Based on the response, show success/failure to the user.