We are the author of the plugin Sales Booster, it provides a feature to allow the customer to add a product to the cart at the last moment, right before the payment in the checkout. (Please see this video for demo: https://screencast-o-matic.com/watch/criqjvViTqo)

However, when used with your plugin there is a minor issue. When a user adds the product to the cart on the checkout page then we call $(‘body’).trigger( ‘update_checkout’ ) internally, this forces the Square plugin to refresh the credit card fields, and now the customer has to fill his credit card again. We would want to prevent this from happening.

It would be great if we can save the credit card fields in JS variables before triggering update_checkout and then fill the fields back after the ajax refresh so the customer doesn’t have to fill them again. We tried this but it looks like the credit card fields are inside an iframe so they are unreadable. Since you have developed the plugin, do you think there is an API that we can use to read and write the credit card fields? Or any other suggestion is also welcome.