How to capture JS varible value sin a different java program

I have a JS program handling the communication from iframe to its parent. I am logging the different states on browser window (Inspect element's) console. How could i fetch these state values into my java program for validating/testing. The values are passed from JS in html file. Or if anyone can suggest any other way to validate the communication between parent and iframe.

Any suggestion or guidance will be helpful to move forward, I am stuck. Thanks alot!!