Express.js - how to ask the server a yes/no question from client?

I'm comfortable in client js, but I'm a server code beginner. Got my site almost all working, but hitting a wall.

In my client, I want the user to answer a question, push a "validate" button, and then the client will ask the Express server "is this the right answer to the question?" and display a checkmark or X next to the input based upon the result.

I can't seem to figure out the right method to do this. The POST examples I see online all use "res.send()" and would refresh the whole page. I come across stuff about promises and ajax, but don't know about those things, and not sure if it's the right road to go down learning.

Can anyone point me in the right direction?

You mentioned you are comfortable in client js. So you should use ajax to make background calls to the server for the validate action you are trying to do. It seems like when you POST, you are submitting and therefore, refreshing the whole page. Then make a route in your express application to handle the ajax request and it won't need to refresh the whole page

Example:
https://www.freecodecamp.org/news/how-to-use-fetch-api/

You can lookup for axios or fetch in the internet.

Here is a tutorial to do it : https://www.geeksforgeeks.org/how-to-send-data-from-client-side-to-node-js-server-using-ajax-without-page-reloading/

And another one about fetch : https://www.freecodecamp.org/news/how-to-use-fetch-api/

To stop the page from refreshing, when the user clicked in the button, you have to prevent the default behavior of the button, you can do this with javascript.

Just a little clue for your research : e.preventdefault()