Saving d3 chart states for users

The project I'm working on involves financial data, my issue specifically pertains to chart visualizations with d3.js. So my back-end is in PHP using Laravel and my front-end will request data through an AJAX call to my back-end and it will send data to the client in the response.

I then use d3.js to visualize the data in various graphs. Because this is async and uses async GET requests, I don't have any specific URL path to navigate to in order to 'save' a state. Navigating away from this page will cause a reset for anything a user might have entered.

I am wondering if there is a way to easily integrate some sort of method for saving a chart's state. I am thinking maybe cookies could be something to look into? The user can add various technical indicators such as moving averages and there is technically no limit to how many indicators they would like to show. As a result, a user can concoct some complex charts--all of which would be reset anytime a user wants to refresh the page or in the off-chance they accidentally hit the back button.

I already have user registration on the website so I could also consider just saving chart states on my end, as well, and fetching them when a user navigates to the charts page. I have access to both a MongoDB database and a MySQL database.

I've never done anything like this before since this is my first time I'm working with a deployed app and the first time I've really needed to consider something like this.

Multiple charts also are depicted on this page, if that makes any difference.