See this - https://developer.mozilla.org/en-US/Add-ons/Setting_up_extension_development_environment - to get a start.

I learned about programming in WordBasic and VBA myself. To target web pages in browsers, you'll want to code in JavaScript and become fluent in the DOM ([https://developer.mozilla.org/docs/Web/API/Document_Object_Model]). Depending on the scope of your needs, a user script might be a quicker way to attack most problems than an extension. Like an Office macro, a userscript runs in a host programming environment (in this case, the Greasemonkey extension) and allows you to experiment freely without a full build cycle (just save script, reload page). There are different APIs you need to learn to convert user scripts to extensions, but depending on your project, that might be overkill. As an example, here's a page about a script I maintain (the code's very improvised, as you might expect when a lawyer writes JavaScript): https://www.jeffersonscher.com/gm/google-hit-hider/ More information: * https://wiki.greasespot.net/Main_Page * https://openuserjs.org/about/Userscript-Beginners-HOWTO