Modal window with a form, how to collect data in the form and send it as a post?

Question

JavaScript

How to perform two form submissions on one click by doing the following?
Form + modal window

(When you click on the "Get a consultation" button, a modal window opens.)
When sending data, the question that the user wrote in the input and the data from the form are sent.

All data must be written to the object and sent in JSON format
Ajax script