REACT App with Sqaurespace website

Hi,

My question is about Sqaurespace website, Reactjs app deployed on Firebase how to connect it all.

I have a sqauresace website + REACT based web app which takes event information from the user,  the data is stored in Firebase and it is displayed . It's deployed on Firebase. It's like an event listing site. So this app has nodemailer, image-resize features. From SEO point of view my sqaurespace website and app are two independent entities. The event list which is the service is not adding benefit to the website. How can i solve this issue?

I read that Squarespace doesn't support server side code and I need to do Setup endpoint/database to be accessible cross-domain via  XMLHttpRequest (I need a little elaboration on how to execute it) Thanks for this post.  But my REACT front end seems to be impossible to transport. 

Any suggestion please.

Thank you

So I need to make an AJAX call to firebase database?