Interested in understanding this codebase and remixing it?
Promise repo
JavaScript bookmarklet code to get URL of tab that was launched from current tab
Start here - https://javascript.info/xmlhttprequest
http://www.kaidez.com/ajax-tutorial/
The seminal article introducing AJAX by Jesse James Garrett, titled A New Approach to Web Applications
how to resolve 404 error
proceeding to section 6 on Ajax and jQuery