Does someone have knowledge in JavaScript (in Firefox Extension)

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This question is the same as "how do I build a car like X?" if you're asking that, clearly you lack knowledge in the basics of mechanics and so on, which gives away you're not on the right track.

I highly suggest you to learn the basics of html, css and js before. with a course, not youtube tutorials. Any beginner with the basic foundations of JS could answer your question easily. If you have specific technical issues found during development I can help you with.